Personalizing breast cancer diagnosis and treatment has resulted in therapies that are more effective and less toxic than in the past.
Image: ThinkstockPublished: March, 2016
The federal government’s “Cancer Moonshot,” with the expressed goal of curing cancer, is getting a lot of press lately. While the initiative’s stated goal may be overly ambitious because cancer is actually 200 or more individual diseases, it promises to increase research funding and speed the availability of new treatments.
Amid the excitement, it’s easy to overlook the fact that there has already been great progress in treating many cancers. Patients are enduring fewer side effects and living longer. Breast cancer is a prime example. “There’s no question that breast cancer treatment is improving,” says Dr. Ann Partridge, senior physician at the Susan F. Smith Center for Women’s Cancers at Harvard-affiliated Dana-Farber Cancer Institute.
Dr. Partridge highlights three ways in which breast cancer care has become more effective and less toxic.
Assessing risk recurrence
“Historically, we have overtreated the many to help the few,” Dr. Partridge says. For example, most women diagnosed with ductal carcinoma in situ (DCIS)—a precancerous condition—have surgery followed by radiation, even though DCIS is unlikely to advance to invasive cancer in three-quarters of the women who have it. That’s because it has been difficult to tell the women who were likely to develop additional DCIS or invasive cancer from those who weren’t. Today, information from laboratory tests to determine whether tumors have hormone receptors or express certain genes is helping doctors identify which cancers are likely to progress or recur and which aren’t. That technology is available for invasive cancers as well as for DCIS. “We are now better able to spare women who are at low risk from some treatments, including surgery, radiation, and chemotherapy,” Dr. Partridge says.
Targeted therapies
Genomics and molecular biology are also contributing to improvements in both quantity and quality of life for women undergoing chemotherapy. Unlike cytotoxic chemotherapy, which kills not just tumor cells but also other fast-growing cells and results in such well-known side effects as hair loss and nausea, targeted treatments home in on molecules that are unique to or overproduced in cancer cells. The result is more effective treatments with fewer side effects. Trastuzumab (Herceptin) and pertuzumab (Perjeta) block the growth promoter HER2, which is overproduced in 20% of breast cancers. Newer drugs, ado-trastuzumab emtansine (Kadcyla) and lapatinib (Tykerb), work somewhat differently, but have a similar effect.
Two drugs that block proteins that stimulate cancer cell growth—palbociclib (Ibrance) and everolimus (Afinitor)—have been approved to treat women with advanced cancer whose tumors have estrogen receptors. They are used with systemic therapies that reduce estrogen levels. “We’re getting much better at understanding women’s tumors and capitalizing on the vulnerability of the tumor,” Dr. Partridge says.
Better supportive care
For breast cancer survivors today, life is longer and better than it was for women who had breast cancer a generation ago. More than 90% of women are alive five years after their diagnosis, and they have fewer side effects. Dr. Partridge notes that surgeons and oncologists are more aware of and attentive to side effects of treatment—including nerve damage, cognitive issues, bone loss, and heart damage—and are taking measures to prevent or minimize them. Today, a woman’s breast cancer care may involve nutrition counseling, exercise instruction, and psychological support for her and her family. “There is more emphasis on taking care of the whole woman, not just her cancer,” says Dr. Partridge.
What the future may hold
Although the Cancer Moonshot may not yield a cure for breast cancer in the next year, it is likely to speed the availability of more effective treatments with fewer side effects. Among its goals are to make promising new therapies available to more patients through clinical trials, to more rapidly disseminate information from research centers to community oncologists, to equalize the standard of care throughout the nation, and to involve patients and their families as partners in their care. Stay tuned.