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• Beginnings
• Pathology and Cytology
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• Treatment and Follow-up
• Radioactive Iodine
• Low Iodine Diet
• Thyroid Hormone Replacement and TSH Level
• Psychological impact of Thyroid Cancer
• Other Related Health Issues
• Women's Issues
• Men's Issues
• Children and Youth Issues

Radioactive Iodine

1. Should patients suck on sour candies after RAI treatment, to stimulate the salivary glands?

   Please comment on the following study.  Based on the conclusions, as well as the comments by Dr. Mazzaferri, will you be amending your protocol in regards to salivary stimulation following RAI treatment? http://www.thyroid.org/professionals/publications/clinthy/volume22/issue8/clinthy_v228_10_12.pdf
   
   Rajaraman (March 2012)
   As Dr. Mazzaferri comments, this study adds to the controversy.  I do not believe that it ends it. We have emphasized hydration more than salivary gland stimulants but do suggest the latter beginning the day after I-131 therapy and for the remainder of the week.  These interesting results of this small study have not changed our practice significantly.
   
   
   Dreidger (March 2012)
   Their protocol makes no mention of attention to fluid intake. I've always suspected that a major component of salivary gland dose occurs at night and, therefore, we instruct all patients to get up at least 3 times to taste something sour anddrink water. Based on Ed Silberstein's work we also place these patients on a 5 day course of Prednisone, 5mg four times daily to minimize radiation-induced swelling.

   The authors speculate that sour-induced salivation may not actually move iodine out of the gland. To the contrary, if one places a therapy patient in front of a gamma camera and then give them a sour stimulus there is an immediate 50% reduction of iodine content in the salivary glands.

   This publiction with be discussed with my colleagues and we will make an evidence-based decision, but I personally think that a change in our current protocol is premature.
    

2. Is it unusual to use a Tg test level as a pre-treatment test to help determine the RAI dose?

   A patient reports that a few months ago she had a TT for papillary cancer and a neck dissection (8 positive lymph nodes of 62 dissected).  Currently, her Nuclear Medicine physician has ordered a Thyroglobulin test (patient having hypothyroid preparation) and then using that resulting Tg level to choose the appropriate dose of the RAI treatment she will have in the week following the test.  We are familiar with dosimetry for ablative RAI dose based on a test dose of RAI, but we are unfamiliar with Tg used for dosimetry.  Please comment on this Tg protocol.
   
   Dreidger (Feb 2012)
   One would need to know more of the details of the case to comment with confidence. However, the current ATA guidelines are leading us  toward the classification of thyroid cancer patients according to our current understanding of the risk of future recurrence. Many factors, including age, gender, history of previous radiation exposure, family history, etc., factor in to that consideration. We would still say that a patient with positive lymph nodes is at moderate risk of a recurrence; at the same time, we have also observed that patients with an undetectable post op stimulated Tg seem to be at very low risk. Perhaps, a low dose ablation with post therapy diagnostic scanning is an effective way of managing such a situation.
   
   Rajaraman (Feb 2012)
   I am also not familiar with such a protocol and am not aware of the evidence behind this.  The level of thyroglobulin post-operatively is affected both by the amount of residual thyroid remnant and disease.  In theory, a very high level (hundreds) would suggest a significant amount of cancer burden remaining post-op and possibly even metastasis rather than simply thyroid remnant in which case a tracer scan with RAI may alter the dose of RAI given for therapy of consideration or further surgical management.

3. Does the TSH rise when using Thyrogen as a preparation?

   When one has a hypothyroid hormone withdrawal for the purpose of Tg testing and/or treatment, it is considered necessary to obtain a TSH level of at least 30 mlU/L for effective treatment or testing.  However, when one has been prepared for Tg testing or treatment using Thyrogen, the level of TSH during the preparation week is less relevant.  Why is that so?

    

   DRIEDGER (February 2011)

   When Thyrogen is used for testing or treatment it is known that the TSH always rises and typically to levels of 100-150; that is the reason for giving the injections. Therefore, there is not a reason to actually measure the value.

4. How long post RAI ablation should a whole body scan (WBS) be done?

   Driedger (March 1/10)

   When to do the WBS post RAI administration depends upon several factors including; whether the patient was prepared by hormone withdrawal or Thyrogen administration, the equipment and particularly the collimators that the nuclear medicine department uses and the dose that was administered. If the patient is hypothyroid then their kidney function is generally reduced by about 30% and it takes longer to clear the background for a good scan. When Thyrogen is used to prepare the patient the background clears more quickly; we now routinely do the scan at 5 days but we vary the protocol and find that a perfectly adequate scan can be done as early as 48 hours. If patients are hypothyroid then optimal imaging should occur at a later time. Some patients may be asked to return for a second scan after another day or two because the physician needs to determine how that distribution of iodine behaves over time in order to determine whether it is significant or not. The frequency of second scans can be reduced by recourse to several measures;
   
   a. if patients are routinely advised to take laxatives in the days between the RAI administration and the scan, then the gut will be cleared and ambiguous abdominal distributions will occur less frequently.
   
   b. if the department has a SPECT/CT scanner (these are gamma cameras with a built-in CT scanner and capable of rendering a 3D image), then ambiguous distributions of RAI can be sorted out at the initial imaging session without need of a second scan on a following day.
   
   
    

5. When should Synthroid and/or Cytomel be re-started post RAI ablation in patients who have had a hypothyroid preparation?

   Driedger (March 1/10)

   Thyroid hormone replacement can be re-started as soon as the thyroid remnants or residual cancer has completed the uptake of 131I from the blood. I always re-start replacement 48 hours post administration of the radioiodine but it could also be done sooner. Definitely, it is not necessary to wait until completion of the WBS. In fact, there is some indirect evidence that early administration of thyroid hormone might improve retention of RAI in the remnant or tumour by decreasing the pressure on the remnant to secrete hormone into the blood stream.
   
   
    

6. Are pets effected by exposure to us following our RAI treatment?

   Chalmers (Dec 1/09)

   Please describe and comment on the JAMA article by Grigsby et al, Radiation Exposure from Outpatient Radioactive Iodine (I-131) Therapy for Thyroid Carcinoma. JAMA, 2000; 283(17):p 2272-2274². In Dr. Gigsby's study, family members and pets wore radiation collection badges for 10 days following the discharge from hospital of a family member who had RAI treatment, to help determine the level of exposure family and pets have to a patient treated with radioactive iodine.
   
   Response
   This paper was intended to quantify the radiation exposure to household members of patients receiving RAI therapy for thyroid carcinoma. The study involved measuring the exposure levels of all household members by having them wear a dosimeter, a portable device that detects and records radiation doses, for 24 hours a day for 10 days. Dosimeters were also placed in various rooms of the household to see which rooms tended to have high radiation levels. The patients enrolled in the study were all being treated for thyroid cancer with doses ranging from 2.8-5.6 Gbq (average dose 4.3 GBq [116mCi]) and released immediately following treatment. Overall, the range of exposure to household members was found to be 0.01-1.09 mSv (average 0.24mSv), the range of exposure to pets was found to be 0.02-1.1mSv (average 0.37 mSv). The authors concluded that the exposure to household members was below the recommendations of the US Nuclear Regulatory Commission (US NRC) of 5.0 mSv.

   One limitation of this criterion, from a veterinary perspective, is that the US NRC limit of 5.0 mSv is based on acceptable levels for human exposure. The acceptable levels of exposure for a pet have not been mandated by the NRC to date. The smaller body size of some pets and the difficulty in enforcing some common radiation safety precautions for pets (for example pets will not wash their hands!) may make this estimation insufficient for protecting the pet from harmful levels of radiation. However, to put this dose into perspective, an x-ray of a pet's chest or abdomen performed by a veterinarian for diagnostic purposes would result in an exposure of approximately 0.39mSv per view.

   The study conducted by Dr. Grigsby did not measure removable activity, and this is commonly accepted to be substantially less than surface doses. For pets in the home with RAI treated patients, removable activity may be of greater concern than surface dose. Due to the strong tendency of RAI to localize in the thyroid tissue once internalized, ingestion of activity could result in some RAI uptake in the thyroid which may destroy some normal thyroid tissue. The ingested dose would have to be substantial (up to 4-5 mCi) to be of great concern for the induction of hypothyroidism. Ingestion of RAI by pets may be more likely than for human family members as pets are unable to wash their hands, are often unsupervised in the home, have a tendency to explore with their nose/mouth, and will commonly groom by licking their coats. For this reason, the RAI treated patient would be advised to wash his/her hands prior to handling a pet in order to limit the surface contamination of the pet. It may also be helpful to limit the pet's access to areas in the home that could be contaminated, such as the sleeping area of the RAI treated patient, even when the RAI treated patient is not in bed. By closing the bedroom door, the pet will not be able to rest on contaminated pillows or bedding, which should reduce the likelihood of contamination of the coat. For those pets that commonly drink from the toilet, the lid should be kept closed following RAI treatment so that the pet does not drink toilet water that is potentially contaminated with RAI excreted in the urine. While the likelihood of a clinically significant ingested dose of RAI by the pet of a RAI treated patient is likely minimal, following the above outlined precautions should further minimize the risk. Overall, if appropriate precautions are taken, with some emphasis on the pet specific measures outlined above, the potential for harmful exposure to pets following RAI therapy of the owner is minimal.
   
   ²http://jama.ama-assn.org/cgi/content/abstract/283/17/2272

7. Are people at risk of exposure to RAI from their cats or other pets – in what way, for how long, and what precautions should be taken?

   Chalmers (Dec 1/09)

   Background:
   Feline hyperthyroidism is a common endocrine disorder affecting older cats. This condition is typically the result of thyroid adenoma or thyroid hyperplasia, both of which are benign. A common treatment for this is the administration of radioactive iodine (RAI), although other treatments exist including medical management with the anti-thyroid medication methimazole.
   
   Response:
   We have performed two studies¹ to investigate the safety of RAI treatment for cats and their families. We were particularly concerned about the possible impact of the RAI on the family members of treated cats following release of the cat from the hospital. Cats are typically housed for 3-10 days following treatment. The duration of hospitalization depends upon the radiation safety guidelines in each region. Since RAI is excreted in the saliva and the urine in treated cats, the grooming and litter box habits of the cat will impact the amount of activity that ends up on the surface of the cat's coat. Removable activity refers to radioactive particles that are on the surface of the cat (as opposed to the activity that is within the thyroid gland inside the cat). Removable activity is of particular concern to human health, as if human family members' hands become contaminated when petting the cat; the activity could be accidentally ingested. We measured the amount of removable activity on cats for the first 10 days following RAI treatment. In this study, we found that for the first 10 days following RAI treatment, the amount of activity on the surface of the cat that could be removed by stroking or petting the cat was on average about 295 dpm (disintegrations per minute) but could be up to 4148dpm in some samples. To put this level into perspective, the State limit for removable activity for a non-controlled area is <1000dpm/100cm2. We concluded that it is prudent to continue to advise owners of treated cats to observe appropriate hygiene precautions in order to minimize the risk to household members. This includes not allowing the cat to sleep on the lap or in the bed with the owners, and washing hands following handling the cat or the litter.
   
   ¹Chalmers HJ, Scrivani P, Dykes NL, Hubble L, Hobbs J, Erb HN. Evaluation of agreement between two instruments in measurements of radiation dose rates in cats that underwent iodine 131 treatment. AJVR 68(4) 2007 p. 354-357.

   Chalmers HJ, Scrivani PV, Dykes NL, Erb HN, Hobbs JM, Hubble LJ. Identifying removable radioactivity on the surface of cats during the first week after treatment with iodine 131. Vet Radiol Ultrasound. 2006 Sep-Oct;47(5):507-9.

8. I am concerned about contaminating my home with residual RAI after my treatment. What precautions should I take?

   Adam (May 7, 2010) Posting to TCC Online Forum
   
   I understand about not preparing food for others but if I don't touch the food by using rubber gloves would this be OK?
   
   Rather than wear gloves, simply rinse your hands first. Of more concern is the possibility of coughing or sneezing on the food.
   
   Do I have to wipe all door handles that I touch to prevent contamination of others. I don't recall seeing anything about that in any publications.
   
   No. Skin contamination is the lowest level contamination.
   
   I am not sure I understand about washing utensils and plates separately. I have a dishwasher that washes and rinses well, would that not be sufficient to avoid contamination as well?
   
   I don't understand it either. RAI washes off everything so easily that I consider a dishwasher to be perfectly adequate. How contaminated are your dishes and cutlery anyway? Apart from your fork/spoon I doubt that there is much RAI in the first place.
   
   Also using the same bathroom is out but what about the shower. Does that not wash away any radiation I emit via sweat so that others can use the shower after me as this will continue the washing action?
   
   Absolutely right.
   
   How long after my dose do you think it would be safe to hire someone to come in and clean my bathroom, and are there any special precautions I should give them?
   
   You need to assess the risks. After a week there is very little RAI left in your body which is why you can be near other people, but if your bathroom is contaminated, it will stay so until the radioactivity decays away - a gradual process over the next few months - or until it is cleaned away.
   
   How can your bathroom get contaminated. Let's define our terms - to me a bathroom is a room with a bath, you probably don't mean that. The room in question may have any of a bath, a shower, a bidet, a basin, a toilet and a your personal effects.
   
   The space between these items is safe and can be cleaned.
   
   The bath: The very small amount of radioactivity present on your body surface dissolves easily in the huge volume of bath water, and when that runs away it takes the RAI with it. The bath surfaces are designed to be non-absorbent and I have never detected contamination on a bath. No action necessary.
   
   The shower: Very similar to the bath, but there may be a mat in the shower that can hold traces of water. Some people urinate in the shower, and if the water is turned off soon after, a small proportion of the RAI urine may stay trapped in the mat. Action: Lift the mat after use and allow to drain, preferably before you turn the water off. Urinate in the toilet for the first couple of days at least.
   
   The bidet: As for the bath. No action necessary.
   
   The basin: As for the bath. The only real contamination risk comes from spitting out your toothpaste. Since your saliva is 7-100 times more radioactive than your urine, there is a real possibility of contamination in the areas that are splashed - mostly the back wall. I
   have measured this contamination in a proportion of my patients, maybe 10%, even thoough I warned them and asked them to be careful. (In reality, you don't have high hopes of a hypo patient taking on huge lists of do's and don'ts). Action: Take care when spitting out and bend down as close to the basin as possible when doing so. Wash the splashed surfaces immediately after for the first couple of days.
   
   The toilet: This may get contaminated from urine spray - a few ladies strongly under the front of the seat, and half of men weakly all over the place! Multiple flushing has no effect on this and just perpetuates the illusion that you are doing something useful. Action: Ladies, wipe the front of the seat with toilet paper and discard. Men, more difficult. Best to urinate sitting down, otherwise clean all splashed surfaces immediately after use for the first few days. Carpeted areas cannot be decontaminated. We use blotting paper (newspaper would do)cut around the toilet as a mat for male patients.
   
   Personal effects: Mostly mouth oriented, especially toothbrush. Action: Rinse well after use. Floss - wrap in toilet paper and flush away. Nose blow - flush away.
   
   In all cases the amount of residual RAI is small and is NOT a radiation risk to anyone else, but it might be a contamination risk if they can ingest enough of it. Frankly, I find it hard to imagine any circumstances in which RAI from any of the situations described above can get into an adult's mouth (unless they are seriously weird, there's probably a website for them). Toddlers are a different matter and may put your toothbrush into their mouth or touch the wet toilet seat and put fingers in mouth.
   
   I cannot see how a cleaner, pregnant or not, could be at risk if you take the minimal precautions listed above.
   
   
    

9. Will I set off the security alarm at the airport if i have recently had RAI treatment?

   Driedger (Aug 8/05, revised Sept 26/08)

   This is a real issue. One of our patients was stopped at the border about 3 weeks after an 131I treatment. We have been told by a patient that she was stopped a full 2 weeks after a diagnostic (ie, low dose) scan. Fortunately, the border guards are now familiar with radioactive therapies and tests.  All patients should be given documentation to help them through the border. After a treatment dose, the radiation is detectable for about a month; this is not to say that there are any risks for the patients, co-passengers or guards, only that they have exquisitely sensitive measuring equipment.

10. Can you tell me more about blockage of the outflow tear drain system?

    Although somewhat controversial, some doctors recommend that patients suck on sour candies or lemons to increase saliva flow and hopefully thereby prevent salivary gland damage following a treatment of radioactive iodine. Following the same logic, would it therefore be helpful to induce the flow of tears such as by cutting onions, and thereby diminish the chances of the after effect of blocked tear ducts? Are there any other precautions one can take to prevent this occasional after-effect?
    

    Morgenstern (May 1/09)

    Normal tears are produced on the lacrimal gland as well as from the Wolfring and Krauss glands of the eye. These tears are secreted onto the surface of the eye itself and help with nourishment, immune protection, and visual function. Blinking of the eyelids pushes the tears across the ocular surface to the inner corner of the eye where a tear drain system lies. Tears enter into the first part of the outflow system known as the canaliculus and then into the secondary outflow system known as the nasal lacrimal sac and duct. They then drain into the nose or back part of the throat.
    
    Traditional thought processes concluded that radioactive iodine sequestered in the tear glands (lacrimal gland ) as it does in the parotid gland of the mouth.  More recent research discounts this theory. This research suggests that the radioactive iodine sequesters only in the second part of the tear outflow system, the nasal lacrimal sac and duct, and does not affect the overall tear production. If a patient experiences increased amounts of tears in the eye after I131 therapy (usually after doses of greater than 150 mCi) it is most likely due to the blockage of the outflow tear drain system (nasolacrimal sac and duct). Unfortunately, increasing the secretion of the tears will likely only increase the tearing symptoms. It is analogous to a blocked drain in your sink. If you turn on the faucet the water will slowly fill the basin. If you increase the flow of the faucet trying to force more water down the drain you will only fill the basin faster.
    
    Attempts have been made to stent the outflow system open prior to I131 therapy but they have been met with only limited success. On a more promising note, we have developed and are working on an ophthalmic preparation to prevent the scarring from occurring. In theory, the medicine would be given prior to radioactive iodine treatment to minimize injury to the outflow system thus preserving normal tear flow away from the eye.
    
    Dr. Morgenstern et al's study "Expression of sodium iodide symporter in the lacrimal drainage system: implication for the mechanism underlying nasolacrimal duct obstruction in I(131)-treated patients" was cited in the Winter 2008 issue of Thry'vors News.

11. Can you provide information about salivary gland swelling due to RAI treatment?

    Why is there sometimes a delayed reaction (often of about 6-8 months) within the salivary glands, to RAI treatment?

    Some patients report that nodules are found (months, even years later) in the salivary glands via ultrasound. Are these nodules related to having had RAI treatment, or completely independent in origin?

     

    Driedger (Apr 1/09)

    The swelling that patients sometime experience is known as 'subacute sialadenitis' and it is a late complication of the radioactive iodine. It usually occurs within weeks to a year from treatment. It occurs in 1-2% of treated patients despite the efforts we make at the time of treatment to keep the iodine levels in the salivary glands as low as possible. In some patients there seems to be a lingering inflammation in the gland and the swelling that inflammation induces results in obstruction of salivary flow through the ducts. In these cases there may be benefit from an anti-inflammatory drug such as Advil for a few weeks.

    The problem seems eventually to settle down, either through control of the inflammation or as a result of the obstructed portion of the gland ceasing to function.

    I don't have data on salivary gland nodules following radioiodine therapy. Certainly, if the patient experienced the symptoms of salivary gland obstruction following treatment, I would not be surprised to learn that scars had formed within the gland. Where that the case, I would expect them to become a permanent part of the gland.

12. What ways can one minimize the negative effects of RAI, such as sucking on sour fruit/candies?

    Driedger (Nov 1/05, revised Sept 26/08)

    Salivary gland damage is the most common side effect of radioiodine therapy. It is not a problem when only diagnostic doses are given. The condition is known as subacute sialadenitis; it manifests as a painful swelling that appears when one begins to eat because small scars from healed radiation damage obstruct the free flow of saliva. It may appear within days or as late as months after RAI therapy.

    Iodine is normally concentrated by and transits through salivary glands. The parotid glands are affected more often than the submandibular glands. The protocols we use are attempts to minimize the damage. Several things may help and physicians tend to use them in different ways.

    What we currently recommend is:

    1. Maintain a generous fluid intake, enough to fill the bladder every 2 hours or so, especially during the night. We always ask my patients to get up at least three times during the first night to drink water. There is an incorrect notion about that drinking fluids will wash RAI out of the system too quickly; most iodine uptake into the remnants happens in the first few hours before stunning begins to intervene and the maintenance of a high RAI blood level beyond that is not helpful to the treatment.
    2. Sour substances stimulate salivary flow and as such will help to flush radioactive saliva from the gland ducts. We recommend generous use of sour candies or a few drops of lemon juice for the first two days after RAI therapy
    3. Salivary gland massage helps to express radioactive saliva from the glands. Patients are instructed to massage the glands with the flats of their hands after a sour stimulus.
    4. The consensus at the 2007 Conference of the Society of Nuclear Medicine was that a 5 day course of Prednisone is helpful to minimize scar formation and future obstruction.
     

    Many patients have read a paper in the Journal of Nuclear Medicine (i.e. Does Lemon Candy Decrease Salivary Gland Damage After Radioiodine Therapy for Thyroid Cancer? Kunihiro Nakada et al). The problem with this report is that the authors did not say what, if any, additional precautions they used. Again, at the 2007 SNM meeting, all experts debunked this publication.

     

    Adam (March 2/08) (forwarded to TCC)

    How long after should we continue to eat sour candies to keep the salivary glands draining? Is it a matter of week or two or months since Salivary Glands can have problems months after RAI?

    This is a big question that has not really been addressed in detail that I know of. Not everyone believes that sour candies are a good idea. I do.

    Some basic facts:

    The salivary glands are small containers that manufacture and accumulate saliva until it is needed. They get what they need directly from the bloodstream and, for reasons that I certainly don't know, they grab iodine at the same time. The result is a small volume that contains iodine that is much more concentrated (hotter) than it was in the blood - between 7 and 100 times more so.

    Two important preventive actions are sour candies and hydration. Both of these have advantages AND disadvantages:

    Sour candies: They cause the salivary glands to empty but they MAY stimulate them into refilling faster - partly negating the benefit. They also upset the natural balance of the mouth and may make you prone to oral thrush.

    Hydration: Some people advocate 'drink plenty'. I hate this expression; it causes far too much grief because no-one knows what 'plenty' is. How much you drink depends on you, the weather, how hard you're working and what your normal drinking patterns are. Drinking too much will just flush the RAI from the body faster, reducing the amount that the thyroid tissue can get at. My advice is to drink a little more than normal. Perhaps use a bigger glass or drink a little more often. A numeric value? Perhaps 10-20% more.

    After you have swallowed your RAI, it goes into the stomach, then into the blood stream. From there it will be taken mainly by 3 organs, the kidneys, the salivary glands and any thyroid tissue that you have. Depending on age and other factors, the kidneys will have got rid of at least 75% and perhaps as much as 90% of the RAI in the first 24 hours. Of the small amount remaining another 75% to 90% will probably go in the next 24 hours

    Now the important bit. Most of the damage to the salivary glands happens while the 'hot' saliva is sitting in them -and- the hottest saliva is while the blood is hottest - the first few hours after swallowing the RAI.  THIS is when the sour candies and hydration are most important.  The importance drops from day to day after that. After 4 to 6 days the importance is probably gone.

    Is that the end of the story? No. The RAI has gone but the effects haven't necessarily shown up yet. Metallic taste, dry mouth and other effects, if they occur, will probably not show for a couple of days, and sometimes a couple of weeks. My suggestions below do not mention the bicarbonate mouthwash, Biotene and all the other supportive suggestions. These are additional and longer term resources.

    My suggestions, presented here for discussion.

    1) You do not need to suck whole candies. A small piece will trigger the glands into emptying and that is all that is necessary. Sucking a whole candy will just stimulate the gland and cause more imbalances to the mouth environment.

    2) You do not need to suck them continuously. I would suggest a small piece of candy every half hour for the first day, then every hour for the next 3 days.

    3) You do not need candy. A grape, a couple of drops of lemon juice on the tongue, some sort of spicy bite - Try beforehand to see what works for you. One possibility is chewing the smallest size of vitamin C tablet you can find - I just tried it and it worked fine for me.

    4) One 'recipe' for maintaining hydration - Find a tiny cup, say about 25ml/ one ounce. Every time you have taken a candy, wait one minute then take this cup full of water, rinse the mouth and SWALLOW. This will help protect your mouth AND be the 'extra' water that you need.

13. Should I have a bowel cleanse before RAI treatment and/or a whole body scan?

    Driedger (Oct 31/06, revised Sept 26/08)

    There is no reason to perform a bowel cleansing (enema) before the (RAI) therapy. The only issue here is that some (and sometimes, quite a lot) of the administered dose ends up in the bowel lumen. For that reason, we recommend a daily laxative to patients for a few days following the therapy administration: nothing dramatic or uncomfortable; typically a 5mg dose of Dulcolax or similar product is all that is needed. Sometimes we have occasion to scan patients as early as 48 hours after the treatment dose and in nearly all cases, the bowel will be clean at that time. Emptying the bowel beforehand or administering uncomfortable cramping doses of laxatives will not facilitate elimination of the bowel activity. Certainly, the quality of the scan is improved if the bowel is clean of RAI at the time of imaging. Those patients who were prepared with l-thyroxine withdrawal, rather than with Thyrogen, will have greater difficulty in achieving complete bowel emptying.

    Adam (Oct 31/06)

    Many thycans, especially the more mobile ones, those who suffer less from 'hypo hell' and those who have a higher fiber diet, will have a reasonable bowel throughput and will get little, if any, benefit from a bowel cleanse.

    Those who aren't in the above groups may well have a sluggish bowel and/or constipation (I'm not sure that there is a difference) and these may retain some RAI at the time of the scan that should, by rights, have been flushed several days ago.

    This RAI will have two effects. Firstly, it will have been sitting in the bowel irradiating the bowel and surroundings with no possible benefit. Secondly, it will show up on the scan and the radiologist could either miss a genuine metastasis because of the bright bowel, or interpret a bright dot in the bowel as a metastasis when it isn't (neither of these two is particularly likely as thyca doesn't generally metastasize down there).

    Of these, the first may not be terribly important unless the amount of RAI is unusually high (and I have seen one). The second is only important if a mis-diagnosis is made - not particularly likely.

    All in all, the best solution by far is a normal(ish) bowel habit. If this is not possible then some gentle assistance throughout the treatment would be preferable to 'dam busting' techniques.

    Some of these ideas (i.e. bowel cleanse) come from doctors who don't know what these things feel like.

14. Can I go to the dentist after having RAI treatment?

    Adam (April 20, 2008)

    I think that there are two issues here, one for me and one for your dentist.

    Your saliva will be radioactive for longer than pretty much anything else in your body. This will only matter to those you are kissing (not peck-on-the-cheek kissing) and anyone working in your mouth. A dentist will be exposed to aerosols when drilling or using one of those horrible ultrasonic cleaning things.

    I would suggest that for this reason you should wait for at least 2-3 weeks after RAI before going to the dentist.

    The second thing is that RAI DOES affect saliva production and your dentist may, depending on what type of work is to be done, want to schedule it differently for some reason. Your dentist should be informed and make his own choice.

15. Does RAI come from the Chalk River Nuclear Site in Ontario? How do patients get exactly the dose the doctor has prescribed, if RAI is constantly ‘decaying’ (diminishing in strength)? Is it better to take it in pill or liquid form?

    Driedger (May 1/06, revised Sept 26/08)

    Yes, (radioactive) iodine comes from Chalk River. I once worked there and it should be a matter of pride for Canadians that AECL currently produces about 70% of the medical isotopes that are used worldwide. This is the only production site in Canada because a nuclear reactor is essential for the process. The process requires the irradiation of a target material followed by extraction of the radioactive iodine in a "hot cell" using robotic technology.

    One orders a precise amount of the iodine for delivery on a given date and calibrated for a specific time. The iodine is delivered either in a pill or a liquid form.  In our department, the liquid form is more economical because the dose can be used for other purposes at another time in the event of a last minute decision not to proceed with the treatment for a given patient. There is no difference in the effectiveness between the dosage forms.

16. What do patients need to know with regard to use of vitamins and supplements in regards to RAI?

    Driedger (Mar 1/06, revised Sept 26/08)

    For those people who are of generally good health and not restricted in their diet for other reasons, vitamins and mineral supplements serve no obvious useful purpose. During a period of illness when appetite is diminished, supplements may be beneficial. We have no evidence of either benefit or harm of supplements in the case of active thyroid cancer.

    I am often confronted by situations in which patients tell me that they are taking a few or many health food preparations. I have no idea what the composition of these preparations is because there are no legal labelling requirements. Accordingly, I recommend that all such supplements be discontinued in anticipation of a radioiodine therapy.

    Those who are about to undergo radioiodine treatments should refrain from taking supplements that contain iodine, at least while they are following the low iodine diet.

    Many preparations also contain calcium and for this reason, it is recommended that they should not be taken at or soon after the daily dose of thyroid hormone.

17. Who should have RAI treatment? Should patients take Cytomel in the weeks leading up to a withdrawal (hypothyroid) preparation for RAI treatment? Why is it, in some cases, that the whole body scan (WBS) is repeated a few days after the first one?

    Driedger (July 1/06, revised Sept 26/08)

    We still actively debate who should/not receive RAI treatment. In some centres most patients receive RAI but in others the treatment is limited to those who are considered to have disease with a higher risk of recurrence. We don't want to do more harm than good and every needless intervention has some level of risk for a complication. Many physicians would agree that small cancers less than 1cm in size do not benefit from ablation unless they are multiple or have some aggressive features. The cutoff size is a matter of debate. Older patients and men are more likely to benefit from ablation. There are a number of recent publications that suggest protocols for a more discriminating selection of patients for ablation and the debate is likely to find some resolution in the next few years.

    Patients ought to recognize that medical decision making is a matter of balancing risks and of avoiding potentially costly interventions that would not benefit the patient. That being said, I would hope that people would be reassured about not needing ablation, when that is the case, and not needlessly worried when RAI is recommended.

    Cytomel is used by some physicians as a short term measure because it is popularly believed that its use reduces the morbidity associated with hypothyroidism. The evidence actually does not confirm this and one study has reported decreased quality of life for patients who use Cytomel. It is a matter of individual physician preference whether to use it or not.  The longer term problem with Cytomel is its short acting nature. If one takes it twice a day, then there will be two intervals between doses when the pituitary gland will produce TSH for a few hours and stimulate any remaining tumour to grow. L-thyroxine, on the other hand, has a half life of about a week and TSH is suppressed around the clock.

    It can make sense to use Cytomel for a few weeks after surgery while the patient is recovering from surgery and the pathology is being confirmed, then withdraw it for 2-3 weeks, ablate remnants and then institute long-term l-thyroxine therapy. Cytomel has no useful role to play if the patient undergoes preparation with Thyrogen.

    The WBS is performed some days after the administration of the treatment dose of RAI. The interval is necessary in order to allow most of the radioactivity to be excreted; if the activity in the body is too high, the camera will be overwhelmed and unable to produce clear images. The exact interval required is a function of the camera and of the state of kidney function. Also, those patients who were prepared for treatment with Thyrogen eliminate the excess activity more quickly and a good quality scan can be performed as soon as two days post treatment.

    RAI is also seen in other parts of the body.  If the patient didn't take a laxative before the scan there will be activity in the bowel. In the chest, radioactive saliva swallowed while the patient is lying down, may pool in the esophagus and appear initially like a metastatic lymph node; this often clears if the patient is given a drink of water prior to immediate rescan. Other times, radioactive soiling on skin or clothing may create a difficulty with the image.

18. What is the correct dose of RAI for treatment/ablation? How is dosimetry used?

    Driedger (July 1/05, revised Sept 26/08)

    The "correct" dose of radioactive iodine is one of those things that we still debate. You would think that with 50 years of experience, we would have that nailed down by now but we don't.

    There are several reasons for the state of affairs:

    Further, the risk issues are not fully known to the treating physician until after the ablation has been performed and some post- therapy information has been obtained in follow-up.

    1. The "30 milliCurie" rule was not based on any considerations of disease or physiology, but on an American regulation that patients receiving larger doses required admission to hospital. At this dose, many patients required 3-4 treatments over several years to achieve complete ablation.. In some parts of the world, a single dose seems to work and we aren’t sure why that is so. This historical regulation seriously prevented  people thinking about what may be the correct dose on physiological grounds.
    2. Since there is a large margin between the effective dose and toxicity from RAI, people have tended not to perform dosimetry in the main. The exception is that in some centres dosimetry is used to ensure that metastatic disease is treated adequately and this usually involves determining what is the maximally non-toxic dose to bone marrow. At these centres, doses of 500mCi and upwards are used in some patients.
    3. For most of us, the pragmatic solution is to administer a dose that is large enough to ensure ablation of remnants in a single dose at least 85% of the time using our local protocols. In our centre, that dose is 100mCi.
    4. There are no randomized, prospective protocols because groups and individuals have not entirely agreed on what is the intent of ablation; is it to destroy the remnants of normal tissue only or to eradicate occult foci of thyroid cancer, the latter needing a larger dose?
    5. In situations with known high risk; eg, metastatic disease, most physicians would immediately increase the administered dose.
19. Under what circumstances would RAI therapy be used to prevent metastases?

    Ezzat (Nov 1/08)

    The decision to administer RAI therapy after surgery depends on a number of factors, including the staging of the cancer. Although there are many different staging systems, the TNM classification system is most widely accepted. This system takes into account age, tumour size (including presence of invasion beyond the thyroid), presence of lymph node involvement and distant metastases. The 2006 American Thyroid Association guidelines for the management of well differentiated thyroid cancers recommend that RAI therapy be given to those with Stage III or IV disease, all those with Stage II disease under age 45 years, most patients with Stage II disease over age 45 and only select patients with Stage I disease. The features of Stage I disease that would warrant RAI are multifocal disease, metastases to lymph nodes, invasion of the cancer beyond the thyroid or into the blood vessels and certain aggressive subtypes. The presence of infiltration of the cancer through the NODULAR capsule is not listed as a worrisome feature. Infiltration (or invasion) beyond the THYROID capsule into surrounding tissue, however, is an important feature and would warrant the use of RAI.
     

20. Who requires RAI?

    Driedger (Feb 1/06, Sept 26/08)

    This is one of the topics on which experts may differ. At many centres, virtually all patients who have a diagnosis of thyroid cancer will receive RAI therapy; others attempt to sort the patients into risk categories; an activity we refer to as “staging”. The factors we consider include tumour size, evidence of aggressive growth and completeness of the resection. One might use RAI treatment even if the tumour was small if there is evidence of aggressive tumour potential.  Nature does not give us any free lunches and it is always our challenge to try to ensure that the consequences of treatment should be preferable to the consequences of the disease.