Women with obesity when they are diagnosed with early breast cancer have a higher risk of recurrence or a second cancer compared to women whose weight is in the normal range and it can be hard to lose weight after being diagnosed with breast cancer. Now, a clinical trial has shown that a telephone-based weight loss program can help patients with breast cancer whose body mass index is in the overweight or obese range lower their weight by a meaningful degree.

The findings, to be reported by Dana-Farber Cancer Institute investigators at the American Society of Clinical Oncology (ASCO) Annual Meeting, set the stage for follow-up research into whether this type of program can extend patients’ survival and lower their risk of a breast cancer recurrence.

“We know that women with obesity when they are diagnosed with breast cancer have a higher risk of dying of the disease, of developing second cancers, and of dying from any cause,” says Dana-Farber’s Jennifer Ligibel, MD, the principal investigator of the trial, who will present the findings at ASCO. “But we don’t know whether helping patients lose weight after diagnosis will improve treatment outcomes. That’s what this study seeks to discover.”

The Breast Cancer Weight Loss (BWEL) trial, a Phase III trial supported by the National Cancer Institute, enrolled nearly 3,200 women from more than 600 cancer treatment centers in the U.S. and Canada. The participants, who had been diagnosed with stage 2 or 3 HER2-negative breast cancer, had completed chemotherapy and radiation therapy (if it was to be administered) and were randomly assigned to receive either a telephone-based weight-loss program plus health education or health education alone. The weight-loss program, conducted by phone, coached patients in reducing their calorie intake and increasing exercise.

Participants’ height and weight were measured when they entered the study and 12 months later. At the 12-month mark, researchers checked the weight of nearly 2,400 patients who were free of breast cancer.

“We found the weight-loss program was highly successful in helping patients lower their weight,” Ligibel says.  Women who received the telephone-based intervention lost an average of 4.8% of their baseline body weight, compared to an average 0.9% increase in body weight among those in the control group.

The findings were especially noteworthy in that they were consistent regardless of patients’ age, race, ethnicity, socioeconomic status, and education level, and type of breast cancer they had.

Within this overall trend, however, researchers noticed some differences in patterns of weight change among the participants. While the weight-loss program was effective in both older and younger patients, younger women experienced a somewhat smaller weight loss. Younger women who didn’t receive weight-loss coaching gained a bit more weight than older participants, so the amount of weight change was relatively similar in older and younger patients.

A similar pattern occurred among Black patients, who made up 13% of trial participants. Black women in the weight-loss program group lost less weight, on average, than others but Black women in the control group gained more weight than control participants of other races and ethnicities. However, women in the weight loss program lost more weight than women in the control group, regardless of their age, race, ethnicity, or other characteristics.

The results provide a lead-in to the next phase of the study. “We’ll continue to follow patients who enrolled in the BWEL trial to determine whether the weight-loss program reduces the risk of cancer recurrence and cancer-related mortality,” Ligibel remarks. “We hope this research ultimately shows that healthy lifestyle change after a cancer diagnosis has a positive impact on outcomes, so we’ll be able to routinely offer this type of program to patients as a part of their breast cancer care.”

This story was published by Dana-Farber Cancer Institute on May 25, 2023. It is republished with permission.