Drug slashes breast cancer rates 50%; results unveiled in San Antonio symposium

In In The News by Barbara Jacoby

LLH network pressBy Jessica Belasco

From: my SA

A study has found an antihormone drug cut the rate of breast cancer by 53 percent in postmenopausal women at high risk for the disease.

The study results were unveiled Thursday at the San Antonio Breast Cancer Symposium.

The researchers who conducted the double-blind, randomized placebo-controlled drug trial said the drug anastrozole may be a new option for breast cancer prevention for some women.

“The results shown here are as good as we could have hoped for,” said Jack Cuzick, head of the Cancer Research U.K. Centre for Cancer Prevention and lead author of the study, published simultaneously in the medical journal Lancet.

The International Breast Cancer Intervention Study II Prevention trial examined 3,864 postmenopausal women ages 40-70 who were at increased risk for developing breast cancer, primarily because of family history.

Half of the women received the drug anastrozole, while the other half received a placebo.

After a little more than five years, researchers found the women who received the drug were 53 percent less likely to have developed breast cancer compared with women in the placebo group.

The predicted cumulative incidence of breast cancer after seven years was 5.6 percent in the placebo group and 2.8 percent in the group receiving the drug.

The study is important because it supports the concept that lowering the estrogen level in women predisposed to breast cancer also lowers the risk of cancer, said Dr. Gladys I. Rodriguez, a medical oncologist at the START Center for Cancer Care in San Antonio who was not involved in the study.

Anastrozole, an aromatase inhibitor that prevents the body from making estrogen, has been used to treat postmenopausal women with hormone receptor-positive breast cancer for more than a decade.

About 80 percent of women diagnosed with breast cancer in the U.S. each year have tumors with high levels of hormone receptors. The hormone estrogen fuels these tumors.

Tamoxifen and raloxifene, two other antihormone therapies, also are used to prevent breast cancer, but anastrozole is more effective and may cause fewer side effects, such as blood clots and uterine cancer, Cuzick said.

The women taking anastrozole (brand name Arimidex) reported side effects including increases in muscle pain and hot flashes, but these were common in the placebo group as well. There also was a significant increase in carpal tunnel syndrome and joint stiffness and a small increase in bone fractures.

“There’s a very general perception that these drugs are very toxic and cause a lot of aches and pain,” Cuzick said. “Ninety percent of the aches and pains had nothing to do with the drug.”

The study also produced an unexpected finding: about a 40 percent reduction in other cancers, mostly skin cancers.

The researchers will continue to follow the study subjects to determine full risks and benefits of the drug.

The pharmaceutical company AstraZeneca provided funding and the drugs for the study. Cuzick is on the speaker’s bureau for AstraZeneca.

The results of the study aren’t too surprising because anastrazole is in the same class as exemestane, another drug that also has been shown to reduce breast cancer among postmenopausal women with a high risk of developing the disease, said Dr. Sharon T. Wilks, medical oncologist with Cancer Care Centers of South Texas, also not part of the study.

“We’re excited that we have yet another type of medication that you can take in pill form that might prevent someone from ever getting breast cancer,” Wilks said. “To know that there’s a reduction over 50 percent in women taking a tablet like this that doesn’t have a lot of side effects is just amazing. It gives us more choices.”

One big question that remains unanswered by the study is how anastrazole stacks up against other drugs proven to prevent breast cancer, Rodriguez said.

In a commentary on the study published in the Lancet, David A. Cameron of Edinburgh Cancer Centre, Western General Hospital in Scotland, questioned whether such drugs translate into fewer deaths from breast cancer and whether they are worth the side effects.

“With the strongest protective effect recorded in hormone-sensitive and screen-detected breast cancers, the overall breast cancer mortality gain with prevention therapy could be small,” Cameron wrote. “No such gain has been reported in any of the pharmacoprevention trials so far.

“Therefore, for any woman considering five years’ anti-oestrogen therapy to reduce her risk of breast cancer without evidence to suggest that she will have a longer life, the perceived and actual toxicity of this intervention becomes important.”

The 36th annual symposium runs through Saturday at the Convention Center. It’s considered one of the leading conferences for advances in breast cancer and draws 7,500-8,000 attendees from more than 90 countries.

It’s presented by the Cancer Therapy & Research Center at the University of Texas Health Science Center, the American Association for Cancer Research and Baylor College of Medicine.