Most women diagnosed with breast cancer have tumors that grow in the presence of estrogen. The anti-estrogen therapies that have been developed to treat these tumors cut the risk for cancer recurrence in half, and reduce deaths by about one-third. Tamoxifen, which has been used and researched for decades, works by binding to the estrogen receptor, which keeps estrogen from getting into the cancer cells to stimulate their growth.
The newer aromatase inhibitors (AI), which include letrrozole (Femara), anastrozole (Arimidex) and exemestane (Aromasin), appear to be even more effective in reducing recurrence and death. The AIs, as they are called, work in a different way than tamoxifen does. These drugs inhibit an enzyme called aromatase, which converts androgens (male hormones) to estrogen. Unlike tamoxifen, which can be used by both pre- and postmenopausal women, the AIs can only be used by postmenopausal women.
Chemotherapy is given over an intense few months after the diagnosis of early-stage breast cancer. In contrast, anti-estrogen therapies must be taken daily for five years to be maximally effective. Newer research suggests there might even be an additional benefit if these drugs are used for up to10 years, or even longer.
Like all other drugs, anti-estrogen treatments have side effects. At least one-third of women on an AI experience chronic joint and soft-tissue pain. Other common side effects include bone loss and vaginal dryness. (These are a result of the estrogen depletion.) Tamoxifen’s side effects include vaginal discharge and hot flashes along with a slightly increased risk of endometrial cancer, blood clots and cataracts. As a result, it’s not uncommon for women to find that they may need to take other drugs to alleviate some of these side effects.
Tamoxifen is also used as breast cancer risk reduction in high-risk women. However, many high-risk women opt not to take it. Studies suggest this is because high-risk healthy women are reluctant to take a daily drug with side effects for a disease they may never get. For them, the risk-to-benefit balance just doesn’t seem to make sense.
Less understandable are findings from a study presented Dec. 11, at the San Antonio Breast Cancer Symposium by Stephen Chia, a medical oncologist at the British Columbia Cancer Research Center in Vancouver, Canada, which showed that an alarming percentage of women who have been diagnosed with invasive breast cancer are not taking the tamoxifen or aromatase inhibitor they were prescribed.
Chia and his colleagues found that nearly 40 percent of a group of 2,403 postmenopausal women prescribed adjuvant hormonal therapies were not taking them. (Actually, this was not the first study to highlight this problem. Prior studies looking at tamoxifen noncompliance found rates of 20 to 49 percent.) In the United States, one factor that must be taken into account is a woman’s inability to afford the medication, as it may not be fully covered by her insurance or she may lack insurance coverage. But this isn’t the case in Canada, where these medications are covered under a national health care plan.
Because this study used data obtained from a retrospective review of pharmaceutical records, the researchers could not ask these women why they didn’t take their daily pill. This means, we can only speculate as to the reasons they did not comply. Was the favorable benefit-to-risk ratio not well explained or understood? Were the side effects too difficult, or not properly attended to by these women’s doctors? Did better quality of life in the present come to matter more than preventing a future recurrence that might never happen? Did the scary specter of breast cancer simply begin to fade over time? Or, were these women just plain tired of treatment and medical care?
So, we’re left with a troubling reality: Even when we do know how to help women diagnosed with breast cancer survive their disease, many of them simply choose not to avail themselves of treatment.
Something else is wrong here. The first session of this year’s meeting, like last year, focused on the results of large, costly randomized trials comparing various sequences and permutations of these anti-estrogen therapies, teasing out the vanishingly small incremental gains. Imagine if a fraction of the millions spent on these trials was invested in discovering why it is that women with breast cancer discontinue taking these drugs. Let’s ask the women themselves.