Transcript The Current Practices and Perceptions of the Low

The Current Practices and
Perceptions of the
Low - Iodine Diet in the Treatment
of Thyroid Cancer
Emily Kwan, B.Sc. (FNH)
Dietetic Intern
Vancouver General Hospital
July 8, 2003
Introduction

Total thyroidectomy - a common initial treatment
for patients with differentiated thyroid cancer

Radioactive iodine (I-131) scanning - to ensure
no residual tumor is present in the neck after the
surgery

I-131 ablative therapy - to destroy cancer
remnants and prevent disease recurrence
Introduction

Important to maximize the uptake of I-131 by
thyroid remnants
– iodine-concentrating capacity of tumor cells is
less effective than normal thyroid cells
– cumulative effect of total-body radiation
--> limits the total amount of radiation one can
receive
Introduction

How does a low-iodine diet "work"?
– iodine - normally absorbed by the thyroid
gland for thyroid hormone production
– a LID depletes the thyroid of its natural stores
of iodine
– when I-131 is administered, the thyroid will
"suck up" the iodine because it has been so
depleted of its natural stores
Current Problems

Some physicians/facilities do not support the
need for dietary modifications prior to and/or after
I-131 scans and treatments

Existing guidelines for LID vary among clinical
studies, physicians, dietitians, and hospitals
offering I-131 procedures
Current Problems

Inconsistencies in the existing guidelines include:
– level of iodine intake restriction
– duration of the diet
– use of diet for scans and/or treatments
– quality of dietary information
• verbal and/or written instructions
• food list (allowed and avoided)
• use of multivitamin or calcium supplements
• use of distilled water
Purpose of the Study

To examine the current practices and perceptions
of physicians and dietitians regarding the use
and efficacy of LID, and to compare them with
the recommendations made in existing literature
Subjects and Methods


Literature Review
– Medline, Pubmed, references cited in pertinent
articles
Electronic Questionnaires
– developed two questionnaires (physicians and
dietitians)
– used a combination of qualitative and
quantitative questions
– reviewed by a physician and three dietitians prior
to distribution
– sent out the web site address of the online
questionnaires via emails/faxes
Subjects and Methods

Electronic Questionnaire (con'd)
– convenience samples of 22 physicians and 24
dietitians
– included at least one physician from each of
the five hospitals (VGH, SPH, SMH, RJH,
KGH) & four cancer centres (Vancouver,
Fraser Valley, Vancouver Island, Southern
Interior) in BC that are involved with I-131
patients
Subjects and Methods

Electronic Questionnaire (con'd)
– included at least one medicine/surgery/
oncology dietitian from the same five hospitals
and four cancer centres
– also included some dietitians from other
provinces due to limited availability of BC
dietitians who would see patients for a LID
• provided insight of what out-of-province
dietitians/physicians would recommend for a
LID
Subjects and Methods

Patient Diet Information
– contacted the Nuclear Medicine Department of
each of the five hospitals by phone
– conducted brief and informal phone interviews
with either the nuclear medicine supervisor or
physician
– received their patient information handouts via
fax after the phone interviews
– also included three diet handouts provided by
dietitians from other facilities
Literature Review

Very limited numbers of studies that examined
the effectiveness of LID in the treatment of
thyroid cancers

Goslings B.M. Effect of a Low-Iodine on I-131
Therapy in Follicular Thyroid Carcinomata. J
Endocrinol 1975; 64: 30P.
– one of the earliest studies that examined the
effect of a LID on thyroid cancer patients
Literature Review

Maxon H.R., Thomas S.R., et al. Low Iodine Diet in I131 Ablation of Thyroid Remnants. Clin Nucl Med
1983; 8: 123-126.

Maruca J., Santner S., et al. Prolonged Iodine
Clearance with a Depletion Regimen for Thyroid
Carcinoma: Concise Communication. J Nucl Med
1984; 25: 1089-1093.

Lakshmanan M., Schaffer A., et al. A Simplified Low
Iodine Diet in I-131 Scanning and Therapy of Thyroid
Cancer. Clin Nucl Med 1988; 13: 866-868.
Literature Review

Each study had its own recommendations on
iodine intake restriction level and duration of the
diet
– LIDs: typically provided 30 - 50 ug iodine/day
– DRI: 150 ug iodine/day
– Average Canadian intake: 1000 ug iodine/day
– Duration of the diet ranged from 4 to 14 days
Literature Review

Maxon et al (1983) and Lakshmanan et al (1988)
also included in their studies a list of foods that
were allowed or not allowed in a LID

High iodine foods should be avoided
– iodized salt, sea salt, dairy products, eggs,
seafood, algae-containing foods, all breads
containing iodates, all red colored foods and
medications, and restaurant foods
Literature Review



All demonstrated a positive relationship between
I-131 uptake in the thyroid and dietary iodine
consumption
– urinary iodine excretion levels were reduced
significantly
– radiation dose to the tumor increased by as
much as two-fold
Shorter retention time of iodine in metastatic tumor
as compared with normal thyroid tissue
Unable to show improved ablation rates
Literature Review

Morris L.F., Wilder M.S., et al. Reevaluation of the
Impact of a Stringent Low-Iodine Diet on Ablation
Rates in Radioiodine Treatment of Thyroid
Carcinoma. Thyroid 2001; 11: 749-755.
– 50 regular diet patients vs. 44 LID patients
– ablation rate in patients following a LID was
numerically but not statistically greater than those
following a regular diet
– recommended routine prescription of LID due to
its potential effect and little cost
– suggested a less stringent diet that simply avoid
high-iodine-containing foods might result in
equivalent outcomes
Literature Review

Pluijmen M., Eustatia-Rutten C., et al. Effects of
Low-Iodine Diet on Postsurgical Radioiodide
Ablation Therapy in Patients with Differentiated
Thyroid Carcinoma. Clin Endocrinol 2003; 58: 428435.
– 61 standard diet patients vs. 59 LID patients
– concluded that a LID with a duration of 4 days is
sufficient to achieve iodine depletion
– the only study thus far that has demonstrated
that a LID could improve the efficacy of thyroid
remnant ablative therapy
Questionnaires




Response rate:
– 36% (physicians), 62.5% (dietitians)
Practices and perceptions of LID varied
significantly between facilities and between MDs
and RDNs within the same facility
All physicians were aware of LID; 6 out of 8
physicians recommended it
7 out of 15 dietitians have had experience on LID
counseling
Questionnaires

LID was not universally prescribed for I-131
scanning

Duration of diet ranged from 5 - 30 days before
the procedure and 0 - 5 days after the procedure

Not all patients were told to remain on the diet
after the I-131 treatment
Questionnaires

Level of iodine intake restriction
– do not usually recommend a specific level of
iodine restriction
– only a few MDs/RDNs reported the use of a
LID that provides 50 ug iodine/day
– more important to simply avoid high iodine
foods
Questionnaires

Verbal vs. written diet instructions
Verbal
Written
Verbal &
Written
Physicians
4
1
1
Dietitians
0
2
5
Questionnaires

Physicians' & dietitians' personal beliefs
– a mixture of opinions
– mostly skeptical about the diet
– important to find a balance between the
benefits of LID and patients' compliance
– excellent educational material is essential
– MDs and RDNs should be consistent with their
dietary advice
Patient Diet Handouts

Foods allowed vs. foods to avoid
– Most LIDs limited or restricted the following high iodine
foods:
• fish and seafood
• seaweed or seaweed by-products
• commercial breads and grain products
• dairy products (some allowed up to 1/2 glass/day)
• eggs (some allowed up to 3 eggs/week)
• table salt
• multivitamin/mineral supplements containing iodine
• red, orange, or brown processed foods and
medications
• restaurant, manufactured, and processed foods
Patient Diet Handouts

Inconsistent diet instructions
– duration of the diet
– use of calcium supplements
– foods allowed/not allowed
– level of iodine intake restriction
– use of distilled water
Patient Diet Handouts

Quality of dietary instructions
– few lines to 10 pages
– some provided sample menus, recipes and
information on where to purchase certain food
products
– some provided detailed information on what
foods are allowed/not allowed in each food
category; some simply provided a list of foods
to avoid
– specified number of servings and serving
sizes of foods for each food category
Conclusion

Inconsistencies of current practices and
perceptions among physicians and dietitians on
the LID have been confirmed by this study
Recommendations

Consistent diet recommendations essential

Duration of diet should be dependent on the
nature of procedure

Verbal instructions should be routinely provided
by MDs

Written diet instructions should be available to all
patients receiving I-131
Recommendations

Referral to RDN if needed

Provide contact info of a RDN

Revise current LID recommendations
– shorter duration - 4 days vs. traditional 7-14
days
– liberalized approach
Recommendations

Liberalize the diet
– avoid high iodine foods
– allow small amounts of eggs, milk & cheese
– do not over-restrict meat, vegetables, fruits,
grains & cereals as they are generally lower in
iodine content
Recommendations

1200 mg calcium carbonate daily

Distilled water not required in GVRD

Inpatients should be put on a LID routinely
SPECIAL THANKS
Angie Bowman
Karol Traviss
Theresa Cividin
Tracey Kerr
Dr. Hay
Dr. Powe
Dr. Worsley
and all the doctors and dietitians who have
participated in the questionnaire study