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The Long View​

After I treat women for breast cancer, they mark off the months until they hit the magic number—five years. They’ve seen headlines and reports that tout five years as the cancer remission milestone. But the truth about breast cancer returning is more complicated than that.

It’s true that reaching five years without another cancer diagnosis can mean survival rates improve. But like everything else with cancer, every person is different. About 80 percent of women diagnosed with breast cancer have what we call estrogen-receptor positive breast cancer. That means the hormone estrogen feeds the cancer’s growth. For these women, medications that block estrogen can help keep their cancer from recurring.

Fighting breast cancer with medication

Tamoxifen is one of the drugs that’s prescribed most often to keep breast cancer from coming back. It works by blocking hormone receptors, so cancer can’t use estrogen for fuel. But it can cause side effects like hot flashes, vaginal dryness or discharge, and mood swings. It’s also linked with less common but more serious side effects—uterine cancer, blood clots, and stroke.

Drugs like anastrozole, exemestane, and letrozole can also help prevent breast cancer recurrence. They stop estrogen production, but they’re generally used only for post-menopausal women. These drugs have fewer side effects than tamoxifen, but they sometimes cause muscle and joint pain. If so, changing to a different medication might alleviate symptoms. They can also cause bone thinning, so some women need to take bone-strengthening drugs along with them. (Sometimes the medications palbociclib and ribociclib are used in combination with these drugs, for women with advanced breast cancer.)

Is breast cancer ever cured?

The accepted practice has been to prescribe these estrogen-blocking drugs for five years. But a study published in November in the New England Journal of Medicine found that breast cancer can continue to recur even 15 or 20 years after the initial diagnosis.

The study evaluated almost 63,000 women with estrogen-receptor positive breast cancer who took estrogen-blocking medication for five years and remained cancer free. The researchers found that after they stopped taking medication, women faced a 10 to 41 percent chance of their cancer recurring. Risks were lowest for women with early stage cancer that hadn’t reached the lymph nodes, and highest for women with more advanced cancer that had reached up to nine lymph nodes.

When my patients hit the five-year mark, we talk about whether they should keep taking estrogen-blocking medication to reduce their risk. Because of the side effects, some women really want to stop taking them. But others like the security of knowing their medication is helping to keep cancer from recurring. Together we consider all of their risk factors and preferences, so they can make the best decision for their future.