ABBA NETWORK

Estrogen therapy is about the last thing you’d expect a doctor to prescribe for a woman with breast cancer: The hormone is famous for coaxing tumors to grow, not shrink. But in a new study, one out of three postmenopausal women with advanced cancer who were given a daily dose of estrogen saw their tumors slow to a stop, and in some cases, even get smaller.

Remarkable science, certainly, but the best part is being able to avoid chemotherapy drugs in a group of women who may have awful side effects without much benefit in terms of survival, says Matthew Ellis, M.D., Ph.D., an oncologist at Washington University School of Medicine, in St. Louis, Missouri.

“I don’t have to give them chemo,” says Ellis with evident satisfaction, after presenting the study Thursday at the annual San Antonio Breast Cancer Symposium, in Texas. “They’re not curable, so the question is, ‘What can I give them to make them feel OK?’”

Why do these metastatic tumors react differently to estrogen than so many other tumors do? The 66 women in the St. Louis study had so-called estrogen-receptor-positive cancer (as do 75 to 80 percent of breast cancer patients), and it had become resistant to the estrogen-lowering aromatase inhibitor (AI) drugs they were taking.

However, some patients may benefit from higher doses of estrogen, he says. Historically, women with breast cancer were treated with high doses of estrogen up until the 1970s, when the estrogen-blocking drug, tamoxifen, was found to be a much more effective way to slow cancer growth.

“My question is, given the size of the study, has it really shown that there may not be some patients who don’t require higher doses of estrogen?” says Ingle, who has done myriad research on breast cancer drugs. About 40,000 women die of metastatic breast cancer — or breast cancer that has spread to other parts of the body — every year, and researchers are hot on the path of new treatment options for women who are no longer benefiting from the available drugs. Other researchers at the San Antonio meeting discussed their efforts to develop drugs that fight metastatic breast cancer at the so-called distant sites, such as the bones and the brain.

Affordability also becomes an issue for women spending years in treatment, often chasing the disease by using experimental drugs not covered by insurance. Indeed, says Ellis, another benefit of estrogen therapy is that it’s a lot less expensive than chemotherapy.