The largest breast cancer treatment study ever says many patients don’t need chemo

A breast cancer diagnosis commonly leads to chemotherapy, a harsh treatment that comes with troubling side effects such as hair loss, pain, vomiting, and fatigue—not to mention the post-treatment, late-developing consequences like heart issues, kidney problems, and infertility, according to the Mayo Clinic. In fact, in most breast cancer cases, the National Institutes of Health recommends adjuvant chemotherapy (chemo that follows other treatments, like surgery). But a new landmark study has found that 70 percent of women in the early stages of cancer needn’t be subjected to the severe option, CNN reports.

In the expansive nine-year study published in the New England Journal of Medicine, researchers aimed to determine whether adjuvant chemotherapy was necessary for midrange-risk patients who have hormone-receptor positive, HER2-negative, node-negative cancer (which affects about half of the women diagnosed worldwide) based on a 21-gene expression test. Remarkably, the results found that those diagnosed early, with smaller tumors that haven’t spread, could still fight off cancer using hormone therapy alone, which typically involves pills or injections—no chemo included.

In the study of 9,719 women aged 18 to 75 who had breast cancer, researchers first scored each participant using the genetic test. Otis Brawley, MD, chief medical and scientific officer for the American Cancer Society, told CNN that the test looks at all 21 genes to see if each is “turned on or off, and then if it’s overexpressed or not.” After getting yes or no answers on each gene, the test “looks at all 21 of those answers and gives that cancer a recurrent score between 0 and 100.” A high score is 31 or higher, and a low score is 0 to 10. Though the medical world agrees low scores don’t require chemo, this test focused on how necessary the treatment is for those with a midrange score.

After nine years, 83.3 percent of those who received just hormone therapy did not see a cancer recurrence, compared to 84.3 percent of those who received chemoendocrine therapy—hardly a significant difference.

In the test, women with a midrange score of 11 to 25 (69 percent) were randomly sorted into two groups: to receive only endocrine therapy (hormone therapy) or to receive chemotherapy plus endocrine (chemoendocrine) therapy. After nine years, 83.3 percent of those who received just hormone therapy did not see a cancer recurrence, compared to 84.3 percent of those who received chemoendocrine therapy—hardly a significant difference.

“I’m delighted. I’ve been worried for a long time about unnecessary treatment for cancer, and unnecessary side effects from chemotherapy,” Dr. Brawley says. “Now with these genomic tests, we are finding that we have multiple types of breast cancer, perhaps several dozen, and we are being able to tailor our therapies to the type of breast cancer every woman has.”

Because of these results, thousands of women will be able to skip chemo every year and focus on a treatment option that works best for their specific type of cancer. Still, always talk with your doc to make the safest choice for you and your body.

This new techy bra might be able to diagnose breast cancer. Or, find out why women of color should start breast cancer screenings earlier.