Biology 103
2001 First Web Report
On Serendip

Tamoxifen is specifically used with patients who have estrogen-receptor-positive breast cancer, because it cuts off the cancer cells' supply of estrogen, thereby slowing the growth of the cancer (2). Tamoxifen is a selective estrogen receptor modulator (SERM) that works by blocking cells' estrogen intake and mimicking estrogen to stimulate other cells within other organs, like the uterus (3).

Breast cancer is the second leading cause of cancer death in American women, and it is estimated that 40,000 American women die each year from the disease (1). Though some risk factors have been determined for breast cancer, such as having a close female relative with the disease or being over 30 years old at the time of the first pregnancy, these factors only slightly increase a woman's chance of developing the disease. Because of the myriad possible risks, no American woman is able to avoid falling under one of the categories. In estrogen-receptor-positive breast cancer, which is the type of breast cancer women in the high risk categories are more likely to develop, tamoxifen has been administered as a postoperative therapy. In some trials, tamoxifen has been observed to prolong some women's lives and reduce the rate of tumor reccurance (2).

Women need more information when it comes to possible risks and benefits of taking tamoxifen. With only a few studies on this drug that failed to address some of the long term pros and cons, it can be argued that doctors relying heavily on this drug as a means of treatment, may be doing so irresponsibly. Without a better understanding of the effects of this drug, patients and doctors alike will not know if the benefits really outweigh the risks.

Though there have been a number of studies done on tamoxifen, in both the United States and Europe, the drug was approved by the Food and Drug Administration, for the reduction of incidence of breast cancer, based primarily on the results of the Breast Cancer Prevention Trial (BCPT) (2). In this study, 13,388 high risk women were divided in two equal groups , one received tamoxifen and the other a placebo. At first the study was double blinded, but five years into it, the study was unblinded due to the "clear evidence of a reduction of breast cancer in the tamoxifen group" (3). After this, members of the placebo group were able to begin taking tamoxifen, making it virtually impossible for researchers to isolate the long term effects of tamoxifen on breast cancer or mortality.

The BCPT concluded the benefits of the tamoxifen to be a reduced five year risk of breast cancer in the surveyed population. And in other studies of the drug, there has been a reduction of mortality from breast cancer. While these are definitely positive findings, it is essential to not overlook, not only the risks of taking tamoxifen, but also that the advantages only persist for at least five years (4).

As with any synthetic drug, tamoxifen has a long list of possible and probable side effects associated with its use. Some of the more mild side effects include nausea, hair thinning, skin rash, and cataracts (5). The chemical make-up of the drug results in other more serious and potentially fatal risks. Blood clots and stroke are two of these possible risks, the other is an increased risk of endometrial cancer due to the increased stimulation of estrogen mimicking cells in the uterus (4). Yet another risk that accompanies the use of tamoxifen is the fact that all tumors eventually build up a resistance to the drug, and it is possible for some tumors to actually be stimulated by tamoxifen (3). And of the limited observations done on the long term use of tamoxifen, women who take it for more than ten years have a potentially higher risk or recurrence and endometrial cancer (3). The risks, therefore, significantly out number the benefits, but at this point in the level of understanding, each patient must determine if the benefits outweigh the risks for herself.

In order for patients and doctors to make an informed decision about taking tamoxifen, they need accurate, consistent, and detailed information about both short term and long term side effects. To date, there are still several unanswered questions about tamoxifen use, and there is no data that supports the use of tamoxifen for more than five years (4). To answer these questions, it seems imperative for a new study to be conducted, one that focuses on tamoxifen use for more than five years and also the long term occurrence and severity of the adverse side effects commonly associated with the drug. This new study should, in contrast with the Breast Cancer Prevention Trial, include a long term placebo group to measure the absolute effect of tamoxifen on the body.

Only time will determine the benefits and risks of this drug, but with more definitive and precise data, patients will be better able to assess whether tamoxifen is right for them. So much remains unknown about how to cure, treat, and ultimately prevent mortality from breast cancer, but conducting more clinical trials will hopefully provide insight on these unknowns. Clinical trials on tamoxifen must be conducted in consideration with the concerns about long term side effects and the severity of these side effects. When patients with breast cancer have to decide whether or not to take a medication that could cause other potentially fatal cancers, like endometrial cancer, having access to statistics would better enable a patient to determine if the benefits really outweigh the risks. If patients stop taking tamoxifen after five years because they run a risk of getting another type of cancer, but the drug has been the only thing keeping them from suffering recurrence, is there nothing they can do but decide what kind of cancer they would rather have? Before doctors pose this catch-22 to their patients, it seems as though they should have some kind of alternative, or at least another type of hormonal treatment their patients could take after the five years with tamoxifen.

WWW Sources

2)Questions about Tamoxifen

3)Position Statement on Tamoxifen, on National Breast Cancer Coalition Homepage

4)Effects of Hormonal Therapy

5)Descriptions of Tamoxifen

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