Two generic drugs shown to reduce breast cancer deaths

In this May 6, 2010 file photo, a radiologist uses a magnifying glass to check mammograms for breast cancer in Los Angeles.

AP Photo/Damian Dovarganes

There's new evidence that two inexpensive generic drugs can improve survival rates for women who develop breast cancer after menopause.

In two large studies published Friday in The Lancet, a class of hormone-therapy drugs called aromatase inhibitors and bone-preserving drugs called bisphosphonates improved survival and recurrence rates in postmenopausal women with early breast cancer.

"It may be that this is a first step in helping us figure out which patients are more likely benefit and which patients are not," Dr. Dawn L. Hershman, associate professor of medicine and director of the breast cancer program at the Herbert Irving Comprehensive Cancer Center at Columbia University and New York-Presbyterian Hospital, told CBS News. "We can strategize to give the medications that are going to give the most benefit and avoid the toxicity and the cost for patients with minimal benefits."

The meta-analyses, conducted by the Early Breast Cancer Trialists' Collaborative Group in Great Britain, looked at the results of numerous studies on hormone therapy breast cancer treatments and bone drugs over a decade.

Two-thirds of breast cancer patients are post-menopausal women with hormone-sensitive tumors, according to researchers. These tumors use either estrogen or progesterone, sometimes both, to grow. Hormone therapy for breast cancer -- very different from hormone replacement therapy for menopause -- works to either block the receptors for estrogen or progesterone on the tumor or works to eliminate these hormones from the system.

"The guidelines have been to use aromatase inhibitors in post-menopausal early-stage cancer that's hormone-sensitive. In terms of the bisphosphonates, I think that it gives us some insight into the fact that agents that affect the bone also effect likelihood of recurrence [of cancer] in the bone."

Though tamoxifen has been used this way for several decades, use of aromatase inhibitors, which destroy estrogens made outside of the ovaries, have become more of a standard for post-menopausal patients. These studies have shown they are more effective at reducing breast cancer deaths and recurrence than tamoxifen.

The 10-year death rate was 12.1 percent with aromatase inhibitors, versus 14.2 percent with tamoxifen. And the breast cancer returned more frequently with tamoxifen than with aromatase inhibitors.

"Aromatase inhibitors have really surpassed tamoxifen in post-menopausal women," said Hershman. "Not only are they slightly better, the side effects are less troublesome."

She added that these results may help researchers think about approaches to treating the cancer "which gives us other targets: the tissue itself as opposed to the tumor itself."

"The impact of aromatase inhibitors is particularly remarkable given how specific these drugs are," lead author of the aromatase-inhibitor study, Professor Mitch Dowsett of The Royal Marsden and The Institute of Cancer Research in London, said in a statement. "Removing only the tiny amount of [estrogen] that remains in the circulation of women after the menopause, and given the extraordinary molecular differences between ER [estrogen receptor] positive tumours."

Though both kinds of therapy have side effects, those from tamoxifen can be more life-threatening. Tamoxifen can increase risk for blood clots in the lungs and legs, stroke, cataracts and uterine cancer, although the most serious side effects are still rare.

"Aromatase inhibitors don't do that -- they have other side effects such as joint discomfort and a slightly higher risk of osteoporosis, which can lead to increased risk of fractures," said Hershman. "I think most people would prefer the aromatase inhibitors because the side effect profile is at least a little less troublesome."

The other set of studies looked at using bisphosphonates, which are often prescribed to post-menopausal women to help protect their bones from the side effects of hormone therapy combined with age-related bone weakening.

The analysis of treatments using the bone-protective class of drugs included 18,766 women in 26 random trials, comparing two to five years of bisphosphonate treatment versus no bisphosphonate. For postmenopausal women, treatment with bisphosphonate reduced the rate of cancer recurring in the bones by 28 percent and also reduced the risk of dying from breast cancer by 18 percent in the first decade after diagnosis.

"The data on the bisphosphonates in terms of the effect on disease-free survival in breast cancer has sort of flip-flopped," said Hershman.

"If you take the two studies together you can possibly have an increased benefit from the aromatase inhibitor and a slightly increased benefit from the bisphosphonate, then the lowering of the fracture risk, which would normally be the side effect of the aromatase inhibitor," said Hershman. "There may be benefits to giving them combined because one is counteracting the side effects of the other."