Hormone Therapy

What are the hormone therapy choices?
If a breast cancer has estrogen and progesterone receptors, which means that these hormones may fuel the growth of these cancers, the treatment options are broader. Tamoxifen, of course, is the gold standard, and this drug is given to women with hormone-responsive breast cancer. It attaches to the estrogen receptor and deprives the cancer of a needed hormone. It thereby starves the cancer cell of a needed nutrient, if you will. The aromatase inhibitors do this by shutting off the residual production of estrogen at sites outside the ovaries. But they're in a sense doing the same thing as tamoxifen.

How much risk reduction is associated with hormone therapy?
Tamoxifen given for five years to women with hormone-responsive breast cancer lowers the risk of recurrence by 40 percent per year, and the overall benefit will be close to a one-third reduction in risk. There is no consistent evidence of benefit with tamoxifen beyond five years. In addition, the risk of developing uterine cancer increases with more exposure, so after five years you get no additional benefit, but you keep adding risk.


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Breast Cancer TestsWhat are the hormone therapy choices?If a breast cancer has estrogen and progesterone receptors, which means that these hormones may fuel the growth of these cancers, the treatment options are broader. Tamoxifen, of course, is the gold standard, and this drug is given to women with hormone-responsive breast cancer. It attaches to the estrogen receptor and deprives the cancer of a needed hormone. It thereby starves the cancer cell of a needed nutrient, if you will. The aromatase inhibitors do this by shutting off the residual production of estrogen at sites outside the ovaries. But they're in a sense doing the same thing as tamoxifen.
How much risk reduction is associated with hormone therapy?Tamoxifen given for five years to women with hormone-responsive breast cancer lowers the risk of recurrence by 40 percent per year, and the overall benefit will be close to a one-third reduction in risk. There is no consistent evidence of benefit with tamoxifen beyond five years. In addition, the risk of developing uterine cancer increases with more exposure, so after five years you get no additional benefit, but you keep adding risk.
The last few years have given us new options in adjuvant hormone therapy for postmenopausal women. It now looks increasingly like substituting or switching to or following that tamoxifen with an aromatase inhibitor further improves outcome.

We have three large randomized trials as of May of 2004, all of which show the same thing: The risk of a recurrence of breast cancer in the breast or a recurrence of breast cancer outside the breast is more greatly reduced when a woman is on a aromatase inhibitor compared to tamoxifen.

How could a postmenopausal woman decide between hormone therapies?
Choosing between tamoxifen, the standard therapy, and one of the newer aromatase inhibitors still remains somewhat tricky. On the one hand, there is no question that the likelihood of events is reduced when you take one of these new drugs over the short run. The big question is what do they do to bone density because aromatase inhibitors significantly lower estrogen, and that decreases bone density.

On the other hand, tamoxifen has some fairly well-described short-term side effects like an increased risk of uterine cancer and aside from that, an increased risk of vaginal complaints like bleeding or discharge. And these things seem to be less of an issue with the aromatase inhibitors. There is also an increased risk of blood clots with tamoxifen, and maybe stroke and even heart attacks. So we have to consider all these issues carefully. Obviously a woman, for example, who has had her uterus removed, has taken away one of the concerns with tamoxifen.

We simply don't know what the very best strategy is, so I think we have to say that doctors and their patients will have to individualize treatment.