Hope for A Cure
After years of baby steps in the march against breast cancer, new research has resulted in a giant leap forward. Doctors who once hoped, at best, to minimize the devastation of this disease are now peppering their conversations with that four-letter word—cure.
"We’re very careful about using words like cure, but I think it’s time to go back to those words," says Eric P. Winer, M.D., director of the breast oncology center at Boston’s Dana-Farber Cancer Institute. Among the changes doctors expect in the next decade: targeted therapies that attack cancer without harming healthy cells, better detection methods, and treatments to prevent the disease entirely. "Breast cancer is going to be different in five to ten years," says Winer. "I believe we could see a 75 percent reduction in death rates, meaning that instead of 40,000 women dying annually, it will be more like 10,000."
The mood of the cancer-research community has shifted noticeably since May, with news of two drugs. While the compounds themselves (Herceptin and Avastin) are promising, it’s the scientific theory behind the drugs that researchers feel will unlock the secrets of breast cancer.
The Breast Cancer Breakdown
Until recently, breast cancer was seen as a single disease, and many woman were treated the same: "Slash, burn and poison," says Los Angeles breast surgeon Susan Love, M.D., referring to surgery, radiation and chemotherapy.
Now scientists believe that the disease should never have been named after body parts in the first place. Cancer, it turns out, is defined by its genetic blueprint, not just its location. Breast cancer is really a collection of a half-dozen, and possibly more, diseases. Some can be defined by their hormonal activity; estrogen and progestin receptor positive cancers may have three or more distinct forms. Another is distinguished by multiple copies of a particular gene, HER2. Finally, a "basal-type cancer"—linked neither to hormones nor HER2—has also been identified.
Pinpointing the specific type of cancer in the breast will allow researchers to develop new drugs that fight tumor cells with fewer side effects or the collateral damage of chemotherapy.
Such therapies are already being prescribed. Herceptin, used in women with HER2-positive breast tumors (particularly aggressive when untreated), binds to certain proteins, blocking tumor growth and harnessing the body’s own immune system to heal itself. In a study by Mayo Clinic researchers, Herceptin plus chemotherapy prevented recurrences in about half of women who would have had a recurrence. But the true potential of this research goes beyond the drug itself. "The fact that we have identified this key pathway implies to me that other agents will be available in the future that may do even better," says Winer.
The war against breast cancer will be won or lost in a Petri dish, as laboratories identify exactly what type of cancer a woman has, so the most effective agents can be prescribed to combat it. "We used to blanket the whole Amazon rain forest with chemicals," says Larry Norton, M.D., deputy physician-in-chief, Memorial Hospital at Memorial Sloan- Kettering Cancer Center in New York. "Now we design molecules to hit a single tree. It’s a new level of detail."
New Avenues of Attack
Recent findings on Avastin have boosted the profile of anti-angiogenesis drugs, which choke off the blood supply to tumors. This drug, FDA-approved to treat advanced colorectal cancer, is showing promise in breast cancer, too. Theoretically, all cancers produce proteins that direct the formation of new blood vessels that ultimately feed tumors. Studies of Avastin plus chemo showed that blocking those signals could starve colon cancer cells, so researchers began to study the drug for treating other solid tumors. A National Cancer Institute study showed that among women with advanced breast cancer, Avastin plus chemo slowed cancer progression by half. Researchers are now looking at long term survival as well as whether the drug can also benefit women with early stage disease.