06/05/2013 10:11 am ET Updated Aug 05, 2013

For Some Women With Breast Cancer, a Long Time on Tamoxifen

At the annual meeting of the American Society in Clinical Oncology, oncologists highlighted the unpublished, updated results of a large, long-term trial from the U.K. involving thousands of women with early-stage breast cancer. The aTTom study findings adds to the emerging consensus that pre-menopausal women with estrogen receptor positive tumors should take Tamoxifen for 10 years, rather than just five, after initial treatment for the disease.

That's a lot of Tamoxifen, because over 70 percent of cases have estrogen receptors. If we forget about pre-malignant conditions like LCIS, for which this drug may be prescribed, and DCIS, which has its own set of statistical issues and concerns, we're talking about approximately 40,000 pre-menopausal women who are found to have invasive breast cancer each year in the U.S, whose doctors will now recommend 10 years of what some in my community used to call "vitamin T."

To be clear -- I'm not suggesting that Tamoxifen's not worth taking. Several large trials support that it significantly reduces the recurrence rate after 10 years in women with hormone-sensitive tumors. Based on the recently-published ATLAS study, it's evident that the drug hinders recurrences and boosts survival in the long term. Rather, my point is that women, and their oncologists, should be asking lots of questions about how this hormonal treatment interacts with chemotherapy, which may also prolong life and is routinely prescribed to many of the same patients.

Tamoxifen is a relatively old pill. The FDA first approved its use in 1977. It delivers partial anti-estrogen effects by binding to estrogen receptors in malignant and normal cells. It carries relatively small but real risks for blood clots, a typically mild form of endometrial cancer and other side effects. Few oncologists, in my experience, talk about women's libido. One problem with Tamoxifen is that the anti-estrogen can alter mood, skin tone, vaginal membranes and other aspects of femininity that some young (and older) women consider undesirable.

A limitation of the ATLAS study -- which was large and well-orchestrated, besides international, is that it didn't separate between women who got adjuvant "extra" treatment with chemotherapy after initial surgery for breast cancer, and those who didn't get chemotherapy. So it's unclear, despite the largeness of that trial involving nearly 13,000 women over more than 15 years, how much Tamoxifen adds to survival in women who've also received chemotherapy.

The same issue applies to the aTTom trial, as best I can tell. In both studies -- ATLAS and aTTom -- too many women with small tumors developed recurrences after 10 years, which is sad news for more than a few of us. It might be that they didn't get chemotherapy. Or it may be a function of their breast cancer subtypes, that weren't ascertained among patients recruited years ago. Or it might be, and is, that we should be trying better drugs for this disease -- until we can prevent it from happening.

My concern may seem technical, or trivial, but it is neither: It applies to hundreds of thousands of women worldwide who, every year, are trying to make informed choices about treatment of the most common form of breast cancer. Despite the attention, and conclusions drawn from these large trials, I'd still like to know if there's a clear benefit to chemotherapy followed by Tamoxifen or if, for some women, just one or the other would suffice.

For more by Dr. Elaine Schattner, click here.

For more healthy living health news, click here.