Although there are a number of potent medicines to fight breast cancer, many women, even those at high risk for the disease, aren't taking advantage of them, according to experts from the Harvard Women's Health Watch newsletter.
An article in the January 2014 issue of the newsletter cited drugs that have become available in the last 20 years, including tamoxifen ( Nolvadex), raloxifene (Evista), and exemestane (Aromasin). Those medicines can reduce the odds of developing breast cancer for many high-risk women.
These drugs have been shown to prevent the occurrence of invasive and pre-invasive breast cancers," Dr. Paul Goss, director of breast cancer research at the Massachusetts General Hospital Cancer Center, told the newsletter. "It isn't just cancer that's prevented. It's precancer and abnormal mammograms. That leads to fewer biopsies." Part of the reluctance to take the drugs, the experts said, involves worry over possible side effects such as blood clots and an increased risk of uterine cancer.
But, Goss said in the article, the drugs have a long-established history of safety and effectiveness. Researchers have studied the effects of the drugs on breast-cancesr patients long before the medicines were considered for prevention. "Tens of thousands of women have taken these medications worldwide, so the side effect profiles are extremely well defined," Goss says.
He also said that the anti-breast cancer medicines are a harder sell because they don't show immediate, concrete effects like drugs to lower blood pressure or cholesterol. "When you show a patient that their blood pressure today is lower than it was—that's a picture of triumph," Goss says. "It's why the patient is putting up with the side effects. I think that's the single biggest reason why breast cancer prevention hasn't prevailed."
All three drugs work against estrogen receptive positive breast cancer, the most common type of breast cancer, which needs estrogen to grow. Tamoxifen and raloxifene are classified as selective estrogen receptor modulators, or SERMs; extemestane is classified as an aromatase inhibitor. Despite the drugs' advantages, though, the Harvard experts say, there's still a challenge in figuring out which women are the best candidates for the medication.
Who should take the drugs? According to the article, "Some women at very high risk for breast cancer should be considered for preventive drugs. These include women withan inherited BRCA gene mutation; a history of radiation to the chest from another cancer (such as Hodgkin's disease or non-Hodgkin's lymphoma); a personal history of breast cancer; a past breast biopsy that showed atypical ductal hyperplasia or lobular carcinoma in situ—precancerous conditions that increase the risk for invasive breast cancer." But experts face a challenge when identifying other possible candidates, including women with a family history of breast cancer.
According to the article in Harvard Women's Health Watch, expert groups recommend SERMs or aromatase inhibitors for all women who are at high risk for breast cancer based on their score on the National Cancer Institute Breast Cancer Risk Assessment Tool (to calculate your risk, visit www.cancer.gov/bcrisktool). However, the threshold score differs by organization: The U.S. Preventive Services Task Force considers you at high risk if your five-year breast cancer risk score is 3% or higher. The American Society of Clinical Oncology defines high risk as a score of at least 1.66%.
Even an expert like Goss, though, isn't certain how extensively the medicines should be prescribed. "I believe in the value of treatments to prevent breast cancer, but I'm not sure where the borders begin and end," Dr. Goss admits. Given this uncertainty, it's important for each woman to discuss with her doctor whether breast cancer prevention drugs are safe and reasonable for her to take, he says. Some women, such as those at risk for blood clots or uterine cancer, probably shouldn't take the drugs, he says. But even for appropriate candidates, It's also important to consider your quality of life while on the drug.
"Typically with breast cancer prevention you're looking at long-term therapy—over years, rather than months. How you are going to feel over those years is important," Goss says. By blocking the effects of estrogen, these drugs can cause uncomfortable menopause-like symptoms, including hot flashes and vaginal dryness. Aromatase inhibitors also can weaken bones (a side effect that can be counteracted by taking bisphosphonate drugs). There is, however, one definite advantage to taking one of the the medicines: the cancer-reducing benefits will continue long after you go off it. "If you take five years of breast cancer prevention medication, you're left with a permanently reduced risk of breast cancer," Goss says. "That's like an insurance policy."
Adapted with permission from a Harvard Womens Health Watch news release citing an article in the January 2014 issue of Harvard Women's Health Watch newsletter. To subscribe to the newsletter, click here.