Radioiodine
Ablation and Treatment for Papillary and Follicular Thyroid Cancer
(By
Douglas Van Nostrand, M.D. Reprinted, with permission, from pages
161-163, 177, and 194 of Chapters 17 and 18 of the book “Thyroid Cancer:
A Guide for Patients”, (Keystone Press, 2004. Douglas Van Nostrand,
M.D., Gary Bloom, and Leonard Wartofsky, M.D. See
http://www.thyca.org/TCGuide.htm)Frequently
Asked Questions
What is radioiodine
ablation?
Radioiodine ablation is radiation therapy in which radioactive iodine
is administered to destroy or ablate residual healthy thyroid tissue
remaining after thyroidectomy.
What is radioiodine
treatment?
Radioiodine treatment is radiation therapy in which radioactive iodine
is administered to destroy or ablate thyroid cancer by irradiating
that tissue.
What is the
difference between ablation and treatment?
Many physicians use “ablation” and “treatment” interchangeably. Other
physicians use “ablation” to mean the administration of radioiodine
to eliminate any normal thyroid tissue remaining in the neck after
initial surgery and “treatment” to mean the subsequent administration
of radioiodine for the elimination of metastatic disease in the neck
or elsewhere.
Why do I have
any thyroid tissue left after my surgery? I thought my surgeon took
it all out.
Although your surgeon removed your thyroid gland, most surgeons leave
behind small amounts of thyroid tissue to minimize any damage to the
nerve that controls your voice box. This nerve is called the recurrent
laryngeal nerve and runs behind your thyroid tissue. Your surgeon
may also leave some thyroid tissue behind to make sure some of your
parathyroid glands remain intact. These glands control your body’s
calcium levels and are usually located within or behind your thyroid
tissue.
Why do I need
an initial radioiodine ablation when my physician believes he has
removed all of my thyroid carcinoma?
Most physicians will recommend that patients with thyroid carcinoma
undergo at least one ablation radiation therapy with radioiodine.
Research and fifty years of experience suggest that the combination
of surgery, radioiodine ablation, and thyroid hormone replacement
can reduce the chances of your thyroid carcinoma recurring. There
are some situations, however, in which your physicians may not recommend
an initial ablation with radioiodine.
What are the
criteria for not receiving an ablation with radioiodine?
Radioiodine ablation may not be recommended depending on several factors.
These include the size of the original thyroid cancer, the number
of sites involved, the lack of any involvement of the borders of the
thyroid or adjacent tissues, and a lack of evidence that the cancer
has spread…
If radioiodine
ablation is recommended, what are its goals?
Radioiodine ablation has four goals.
First, and for most patients it will reduce the chance of the thyroid
cancer recurring….
Second, destroying the remaining thyroid tissue will improve the ability
of the radioiodine whole body scan to monitor you for evidence of
any recurrence of the cancer…
The third goal is to facilitate the use of the blood levels of thyroglobulin
to monitor you for metastasis. Normal thyroid tissue also produces
thyroglobulin, and thus, in the presence of normal thyroid tissue,
changes in your blood thyroglobulin levels are not as reliable for
indicating spread of your cancer….
The fourth goal is to enhance the effectiveness of future radioiodine
treatments, if needed…
Side
Effects of Radioiodine
- Potential side
effects will vary depending on the dosage of the radioiodine administered.
- In regard to
selecting dosages for radioiodine ablation or treatment, three points
should be remembered. First, the type, frequency, and severity of
side effects must be weighed against the benefit of the dosage for
ablation or treatment. Second, although your physicians may know
the potential risks and benefits of the various dosages, they cannot
predict what will happen in a given patient. Everyone responds differently
to radioiodine ablation or treatment, which often makes it difficult
for a patient to decide which dosages might be best for him or her.
Your personal physician is likely your best resource to help you
make this decision…
- [Some examples
of potential side effects include nausea and vomiting, dry mouth,
change in taste (in as many as a third of patients, typically lasting
several weeks), salivary gland swelling and pain, and drop in blood
counts, and others.]
- As a general
rule, side effects increase in frequency and severity with repeated
or larger doses of radioiodine.
- We do not believe
that any strict upper limit of total cumulative dosage … should
be used. We believe that many factors must be weighed including
but not limited to (1) the severity of the disease, (2) the location
of the disease, (3) whether the metastasis takes up radioiodine,
(4) how the patient has previously responded to radioiodine, (5)
how long ago the last treatment was administered, (6) the total
blood counts (7) what was the response of the blood counts to the
last radioiodine treatment, (8) the age of the patient, (9) the
patient’s other health problems, if any, and (10) other options
available to the patient.
- [Regarding
side effects] keep in mind three things:
- Many of
these side effects are infrequent
- Most of
the side effects are manageable.
- The risk
of the frequency and severity of the side effects must be weighed
in light of the severity of your thyroid cancer.
Last
updated: Oct. 23, 2006
