I have been diagnosed with thyroid cancer, and have for many years
eaten soy foods. I’ve been told that soy consumption increases
the risk of thyroid cancer. Is this true? Could soy foods have caused
my cancer? If not, what might have caused it? Am I going to die?
Thanks for your help,
Susan
Dear Susan,
I am sorry to hear of your cancer. Life sure can throw us some curve
balls, can’t it? Then it’s up to us as to how we respond.
The bad news is that thyroid cancer requires treatment and lifelong
monitoring, and can have some pretty difficult effects on patients.
The good news is that survival rates are high, with 95% of all thyroid
cancer patients in the United States achieving long-term survival
without reoccurrence.
There are four main types of thyroid cancer: Papillary, Follicular,
Medullary, and Anaplastic.
Papillary cancer is the most common type of cancer (60-70% of all
cases), perhaps because papillaries are quite common in the thyroid
gland. Papillary cancer mostly involves one side of the thyroid
and sometimes spreads into the lymph nodes. The cure rate is very
high.
Follicular cancer, the second most common type of thyroid cancer
(10-15% of all cases), is somewhat more malignant than papillary.
The thyroid gland is comprised of follicles which produce thyroid
hormones that are essential for growth and development of all body
tissues. This cancer doesn't usually spread to the lymph nodes,
but it may spread to arteries and veins of thyroid gland and more
distantly (lung, bone, skin, etc), though that is uncommon. Follicular
cancer is more common in older people. Again, the long -term survival
rate is high.
Medullary thyroid cancer is much less common (2-8% of all cases),
and usually originates in the upper central lobe of the thyroid.
It spreads to the lymph nodes earlier than papillary or follicular
cancers. It differs from papillary and follicular cancer, however,
in that it does not arise from cells that produce thyroid hormone,
but instead from C cells. These C cells make the hormone calcitonin.
This type of cancer can run in families, and also has a good cure
rate.
Anaplastic is the most serious thyroid cancer. It appears in 5-10%
of all cases. It can spread early to lymph nodes, thus usually the
cause for a visit to the doctor is a mass in the neck. It also is
the form of thyroid cancer most likely to spread to other organs
beyond the thyroid or lymph nodes. This type of thyroid cancer is
more common in those over 65 and in men. Long-term survival rates
are unfortunately far less than for the other three types of thyroid
cancer.
Some animal studies have shown a link between soy intake and the
development of goiter, but no such link has been found in human
studies. (Goiter is the enlargement of the thyroid gland, causing
swelling of the neck. The primary cause of goiter in humans is a
deficiency of dietary iodine, which is necessary for the production
of thyroid hormone. The gland enlarges in an attempt to increase
the output of hormone.)
In November, 2001, Pamela Horn-Ross from the Northern California
Cancer Center announced the results from a study of soy intake and
thyroid cancer risk. In the study, both total soy consumption and
the intake of individual soyfoods were found to be protective against
thyroid cancer. In contrast to what you have heard, it appears likely
that soy consumption actually decreases the risk of thyroid cancer.
This is consistent with the many studies that have found soy intake
to lower the risk of breast cancer and prostate cancer. I would
have to say it is very unlikely that you consumption of soy foods
has had anything to do with the development of your cancer.
A more likely cause is exposure to radiation. Ionizing radiation
causes changes in the genes of the thyroid cells, and is a widely
recognized risk factor for thyroid cancer. People who received radiation
to the head and neck area when they were young (under 30 years old)
are at highest risk. This practice has been largely abandoned in
medical circles (apart from cancer therapy) for this very reason,
but it was formerly used as a treatment for a wide range of conditions,
including many trivial ones. Japanese atomic bomb survivors have
a much higher-than-normal rate of thyroid cancer, as do those exposed
to fall-out from Chernobyl. Flight attendants and pilots also have
increased rates. Slow growing thyroid cancers often take 10 - 30
years after the radiation exposure to become apparent.
Another established risk factor for thyroid cancer is higher weight.
One study found that women who weigh more than 132 pounds have 2.5
times the rate of thyroid cancer compared to those weighing less
than 114 pounds. On the dietary front, risk factors include diets
deficient in selenium, and those either deficient in or providing
too much iodine. Many studies have found a protective association
for vegetables and fruits.
I do wish you all the best in your journey with cancer. I know how
frightening it can be. The Dalai Lama has spoken about "turning
adversity into one’s ally." This is easier said than done,
of course, but I do like to keep the concept in mind when dealing
with difficult circumstances.
Are you going to die? I think we can be 100% certain that you will.
Will it be as a result of your cancer? Probably not. But in the
mean time, given that you and I and everyone we know will someday
die, it might not be a bad idea to make the most of every precious
second.
