Index to this Health
Guide
Introduction
Types of Thyroid Cancer
Radiation Exposure
Treatment
Radioactive Iodine Therapy
External Radiation Therapy
Post-Treatment Check-Ups
Summary
Questions and Answers |
Health
Guides on Thyroid Disease
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Introduction
Thyroid cancer which
affects approximately 15,000 individuals annually in North America
is not very common. However, it is common enough so that patients
should be aware of that possibility, particularly for those who
have a nodule (i.e. a localized swelling) in the thyroid gland (see
Health Guide #4 - Thyroid Nodules). In contrast
to other cancers, thyroid cancer is almost always curable. There
are different types of thyroid cancer but the commonest (which occurs
in 80% of cases) is known as papillary, follicular or mixed papillary
and follicular forms. There are uncommon types affecting the thyroid
such as lymphoma, medullary cancer and anaplastic cancer. Thyroid
nodules are more common in females than males; however, males have
a greater risk than females for cancer occurring in a thyroid nodule.
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Types
of Thyroid Cancer
The common types of
cancer respond well to treatment. Except for the rare medullary
thyroid cancer, the occurrence of malignancy among members of the
same family is extremely unusual. Patients with medullary cancer
should ensure that family members are appropriately tested by both
clinical and biochemical tests at an early stage even when no thyroid
nodules are detectable. Medullary cancer may also be associated
with simultaneous involvement of other endocrine glands such as
the pituitary, adrenal, pancreas and parathyroid glands. Such involvement
is known as multiple endocrine neoplasia syndrome.
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Radiation
Exposure
Previous exposure to
head and neck irradiation in childhood, adolescence or even adulthood
has been recognized as an important contributing factor for the
development of thyroid cancer. Years ago, patients received x-ray
treatments for acne, skin problems of the face, tuberculosis in
the neck, fungus diseases of the scalp, blood vessel tumors of the
face, enlarged thymus, tonsillitis, sore throats, chronic coughs,
and even excess facial hair. Such therapy is NO longer performed
for these problems because it became recognized that the thyroid
gland is particularly sensitive to the effects of radiation resulting
in thyroid tumors with a 30% risk for cancer. In addition, patients
who require radiation for the treatment of certain types of cancer
in or near the head and neck area may also have an increased risk
for the development of thyroid nodules and thyroid cancer. If you
have had radiation for any such problems, then consultation with
your physician would be appropriate to ensure that your thyroid
gland is functioning normally and does not have any nodules. |
Treatment
To confirm whether
a thyroid nodule is present, thyroid scanning and ultrasound
imaging procedures are used. However, a fine needle aspiration
biopsy is the BEST diagnostic measure by far to detect which
nodules will require surgical intervention because of overt
or suspect cancer and exclude those which do not. The most effective
form of initial thyroid cancer therapy is surgery (see Health
Guide #11 - Surgical Treatment of Thyroid Disease). Because
of the excellent outlook for most thyroid cancers, some surgeons
feel that it is sufficient to remove only a portion of the gland.
However, there is a growing body of evidence based upon long
term follow-up which indicates that it is worthwhile to remove
as much of the thyroid gland as is safe. This more aggressive
approach will avoid recurrences and optimize subsequent non-surgical
measures such as radioactive iodine therapy. Although a total
thyroidectomy slightly increases the risk for possible deficiency
in calcium by the inadvertent removal of nearby parathyroid
glands, this risk should be minimized when the thyroid cancer
surgery is performed by an experienced surgeon. The potential
for vocal cord damage is also extremely rare in experienced
hands.
In about 30% of
patients, the cancer may spread from the thyroid gland to lymph
glands nearby in the neck. If this occurs, the lymph glands
should be removed by an operation called a neck dissection.
The extent of the removal depends in part on how many lymph
nodes appear affected by the cancer. Usually this can be achieved
through cosmetically satisfactory incisions. Occasionally, the
incision may have to be elongated. Apart from some transient
swelling of the face, the removal of such lymph glands results
in NO serious bodily deprivation or dysfunction.
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Radioactive
Iodine Therapy
Depending on the findings
at the time of surgery, radioactive iodine may be considered post-operatively.
Radioactive iodine is administered in either a capsule or liquid
form usually 6 weeks after completing the necessary surgery. In
order for the radioactive iodine to work, thyroid replacement (tablets)
are withheld during this time. Unfortunately, the patient must endure
the consequences of an underactive thyroid which may include fatigue,
muscle cramps, puffiness and constipation. However, knowing it is
absolutely necessary and that thyroid replacement will begin at
the completion of treatment helps patients deal with this consequence.
In research studies, patients receiving human TSH injections have
not had to stop their thyroid tablets. Hopefully, this material
will be available for general clinical use in the near future.
Radioactive iodine therapy
is simple but depending upon dosage may require isolation in a hospital
room for several days. Although transient neck discomfort, decreased
saliva formation and alteration in taste may rarely occur, there
are usually no significant side effects. Occasionally this treatment
is repeated if residual or recurrent thyroid cancer is detected.
When radioactive iodine is administered at well established dosage
and treatment intervals, over 50 years of experience has indicated
that it is relatively safe with few serious early or late side effects. |
External
Radiation Therapy
X-ray radiation from an external
source by "cobalt beam" is rarely necessary but could
be recommended when the thyroid cancer cannot be completely removed.
External radiation is administered over a 4 to 6 week interval in
small divided doses to the neck region and may induce a secondary
skin reaction due to the formation of small blood vessels and pigment
darkening of the skin. However, this does not invariably occur.
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Post
Treatment Check-ups
Following surgery and radioactive
iodine therapy, thyroid hormone pills are prescribed. Thyroid hormone
not only ensures proper metabolism but suppresses the pituitary
hormone, thyrotropin (TSH) which can stimulate thyroid cancers to
grow. Unlike patients with an underactive thyroid, thyroid cancer
patients are treated with dosages sufficient to maintain the serum
TSH level below normal to prevent further growth of the cancer.
The level of thyroid function is checked periodically by both clinical
examination and laboratory tests. Thyroid cancer patients are examined
at regular 6 to 12 month intervals to ensure that there is no evidence
of recurrent cancer. Measurement of serum thyroglobulin (the precursor
of thyroid hormone) is the single best test to determine whether
recurrences have occurred. Neck ultrasounds and chest x-rays may
also be required to ensure that the cancer has not persisted or
recurred.
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Summary
For the commonest forms of papillary
and papillary-follicular thyroid cancer the 5 and 10 year survival
rates are IN EXCESS OF 95%. The risk for recurrence is higher in
patients over the age of 45 or if the thyroid cancer has extended
outside of the thyroid gland at the time of the original diagnosis.
However, early detection and treatment often averts such consequences.
Patients usually have questions regarding
thyroid cancer. Here are some of them. If you have a different question,
you might write to the Thyroid Foundation of Canada and answers
may be published in the Thyrobulletin by a consultant doctor.
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Questions
and Answers
- QUESTION:
Does smoking or drinking cause thyroid cancer?
ANSWER: Smoking and drinking
are not related to thyroid cancer. Such habits of course are
better avoided for overall good health but they neither cause
nor aggravate the course of thyroid gland malignancy.
- QUESTION: Does thyroid
cancer spread throughout the body and how can you tell if this
is so?
ANSWER: Thyroid cancer
rarely spreads throughout the body. Most thyroid cancers are
cured by the initial operation. Although thyroid cancer may
extend to lymph glands in the neck, the removal of these lymph
glands is usually quite feasible and curative. Infrequently
cancers do spread to lung and bone and can be detected by x-ray
and scanning imaging procedures. Such a situation requires treatment
by radioactive iodine or other x-ray therapy procedures and
occasionally surgical removal. For the rare but more aggressive
types of cancer, treatment with chemotherapy and x-ray therapy
may be recommended.
- QUESTION: How likely are
my chances of dying of thyroid cancer even with all this treatment?
ANSWER: Other than skin
cancer, the most common types of thyroid cancer have the best
longterm outcome when promptly treated compared to all other
types of cancer. Almost all patients are totally cured by treatment.
- QUESTION: How is thyroid
cancer detected?
ANSWER: Thyroid cancer
is frequently detected by the patient becoming aware of a lump
in the neck. Half such cases are detected by a physician during
a routine physical examination for an unrelated problem. Thyroid
cancer does not cause pain and rarely produces symptoms. Virtually
all patients with thyroid cancer have normal metabolism and
thyroid tests.
QUESTION: What are the side
effects of treatment? Will I lose my voice or have a large scar?
ANSWER: The usual treatment
of thyroid cancer involves the removal of at least a portion or
all of the thyroid gland through a small neck incision. It is
infrequent for patients to have any problem with a voice disorder
or calcium imbalance as a consequence of the surgery. The removal
of lymph glands may require a larger incision, but this is usually
low in the neck and is still compatible with a good cosmetic result.
QUESTION: What can I do to
ensure that I have the very best result of treatment for my thyroid
cancer?
ANSWER: It is important
that nodules in the thyroid gland or in the neck area be appropriately
diagnosed at an early stage. You should see your family doctor
who will assess the situation and most likely refer you to the
appropriate specialist to confirm the diagnosis and administer
the correct treatment. However, in contrast to many other cancers,
early detection and treatment almost always results in a complete
eradication and cure!
- QUESTION: Will I have to
stop my thyroid tablets if radioactive iodine is being given?
ANSWER: Yes, for 6 weeks.
The only way the radioactive iodine can "get into"
the thyroid and work is if your TSH level becomes elevated.
This will occur when you stop your thyroid hormone. Unfortunately,
during this time you will likely experience the effects of an
underactive thyroid which may include fatigue, muscle cramps,
puffiness and constipation. Research trials using human TSH
injections look promising. Hopefully, once this agent is available,
patients will be able to undergo radioactive iodine treatment
without having to stop their thyroid replacement.
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Written by: Irving B. Rosen, MD.,
FRCS(C), FACS, Professor of Surgery, University of Toronto, Department
of Surgery, Mount Sinai Hospital; Consultant in Surgery, Princess
Margaret Hospital, Ontario Cancer Institute.
Paul G. Walfish CM, MD, FRCP(C),
FACP, FRSM., Professor of Medicine, Pediatrics and Otolaryngology,
University of Toronto; Senior Consultant, Endocrinology and Metabolism
and Head and Neck Oncology Program, Mount Sinai Hospital.
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A
printed version of this Health Guide is available to health care
professionals and the public. For more information call the National
Office or contact your local
chapter.
Production of
the printed version of this Health Guide was made possible through
partial funding assistance from Health Canada. The views expressed
herein are solely those of the authors and do not necessarily represent
the official policy of Health Canada. |
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