According to USNews and World Report, only six percent of women who are at high risk of breast cancer agreed to take the cancer preventing drug Tamoxifen.

The dirty little secret: A lot of these women have heard about the side effects, and said no way.  Who wants to give up a healthy sexual relationship just to (maybe) cut down your risk of getting a cancer that you might get anyway?

Tamoxifen has been around for thirty years, but was usually used only for certain breast cancers (those which were estrogen positive, that is, those cancers that tended to grow if the woman had estrogen in her system. The Tamoxifen blocked the estrogen, so the cancer tended not to grow, or to grow more slowly). Often it was given with other anti cancer medicines, or after a relapse in the disease to prolong life.

In such cases, the side effects seemed to be acceptable, compared with the alternative.

You can read about the side effects HERE: essentially they are the same as putting the woman through menopause: hot flashes, headaches, nausea, fluid retention, depression, weight loss, weight gain, and vaginal problems.

But there are a few rarer but serious problems from taking the medicine long term, including bone pain and fractures from calcium loss, blood clots, and cancer of the uterus.

For younger women, taking Tamoxifen is a problem, because fetal defects in animals has been found; in humans, a few cases of  malformations also have been noted, but there have been too few cases to confirm the actual risk. The real danger is miscarriage, although studies to see if it could be used to induce abortion showed that it wasn’t really very good, even when it was used with other medicines to cause abortion .

Ironically, Tamoxifen has been used to help women who can’t ovulate (produce eggs) to get pregnant.

But what if you are in the “high risk” group for breast cancer? Should you take Tamoxifen?

Who is “high risk” for breast cancer? After all, ten percent of American women will be diagnosed with breast cancer during their lifetime.

But if you have one or more close relatives with breast cancer, you have no children or your first child over age 30, if you started menstruating early or had menopause later than the average woman, if you have had previous biopsies of the breast, especially if it showed “atypia”, then you are at high risk. The highest risk factor is two or more first degree relatives with breast cancer (mother, sister), have had an abnormal biopsy, and are an older lady.

And of course if you are one of the rare people with a positive genetic test, you are high risk. Five to ten percent of women with breast cancer fit into this risk group. Some of these genetic risks also increase the risk of other cancers, such as ovary or colon cancer, so family history is important to figure out who to test.

There are screening tests to figure out your risk LINK.

But lots of women fit into those categories, so you probably need to talk to your doctor about it.

So how well does Tamoxifen prevent breast cancer?

It cuts the chance of getting cancer by half.

Tamoxifen reduced the risk of invasive breast cancer by 49% (two-sided P<.00001), with cumulative incidence through 69 months of follow-up of 43.4 versus 22.0 per 1000 women in the placebo and tamoxifen groups, respectively.

That last part gives a better idea of the benefit. If 100 high risk women didn’t take Tamoxifen, over five years 4 of them would get cancer. But only 2 of the 100 taking Tamoxifen would get cancer.

Problem? This is only over five years. What if you are thirty? Do you take it for the next 49 years until you die? And what about those rare side effects like blood clots and osteoporosis and uterine  cancer? Will these risks show up after many years of use?

Denial of your chance of getting cancer is easier for most women, especially when faced with the list of side effects. The chance of cancer is small ( or not much higher than “average”),and anyway, if one gets cancer, won’t a mammogram pick it up?

Ah, that is the questions. Mammograms are not 100 percent accurate, and may not pick up aggressive breast cancer early.

But the real reason most of us suspect women are not too eager to take Tamoxifen is that they fear premature menopause: getting old before one’s time, and loss of sexual desire. What good is living if you are old, ugly, and unloved?

Reality check. In studies of breast cancer patients, scientific studies assure us that the loss of libido on Tamoxifen is no worse than any other woman with breast cancer. Most of my patients taking Tamoxifen for breast cancer manage. Yet I have run into patients whose marriages were badly affected by Tamoxifen’s side effects, and a quick look at less scientific “discussion boards” suggest that some patients just might not be bringing this up to the physicians when the studies were done.

If this is your problem, the ordinary romantic things often will help; one of my mentors assured me that 80 percent of a woman’s libido is found above the neck; not quite true, but for the other twenty percent, local estrogen creams, and maybe testosterone patches could also help.

Would I recommend you take Tamoxifen? Well, if every woman in your family dies of breast cancer, you might want to talk it over with your doctor.


Nancy Reyes is a retired physician living in the Philippines. She writes medical essays in Hey Doc Xanga Blog, and blogs at Finest Kind Clinic and Fishmarket.

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