A telephone-based weight loss intervention improved physical function and other patient-reported outcomes among women with early-stage breast cancer and overweight or obesity, according to findings from the health outcomes (HO)-1 substudy of the phase III Breast Cancer WEight Loss (BWEL) trial, which will be presented at the 2026 ASCO Annual Meeting (Abstract 12010). Benefits—including gains in physical, mental, and social well-being—were maintained throughout the 2-year intervention period.
During a press briefing ahead of the meeting, presenting author Jennifer A. Ligibel, MD, FASCO, Director, Leonard P. Zakim Center for Integrative Therapies and Healthy Living, Dana-Farber Cancer Institute, said obesity is associated with poorer outcomes in early-stage breast cancer, including higher mortality, worse quality of life, reduced physical function, and greater treatment toxicity. Although prior studies suggested weight loss may improve quality of life, they were small and largely limited to a few institutions.
“The BWEL program was delivered to more than 1,500 participants enrolled from across 635 oncology practices in the U.S. and Canada,” she said in an ASCO press release. “These findings thus show not only that weight loss provides meaningful benefits for people who have both breast cancer and obesity, but also that this can be achieved in thousands of patients enrolled across many kinds of oncology practices.”
Press briefing moderator Julie R. Gralow, MD, FACP, FASCO, Chief Medical Officer and Executive Vice President of ASCO, added, “The BWEL study is challenging us to stop viewing lifestyle interventions as just optional add-ons and start integrating them as standard components of a comprehensive survivorship care plan.”
Study Details
A total of 3,180 patients were enrolled between 2016 and 2021. Eligibility criteria included diagnosis of stage II to III hormone receptor–positive/HER2-negative or triple-negative breast cancer occurring within the previous 14 months, completion of surgery and any indicated chemotherapy and/or radiation therapy, and overweight or obesity (body mass index ≥ 27 kg/m²). The study population was randomly assigned in a 1:1 ratio to receive either health education alone or in combination with a telephone-based weight loss intervention.
The intervention paired each patient with a Dana-Farber–based weight loss coach and included up to 42 telephone sessions delivered over 2 years. Patients received individualized calorie goals designed to produce a 500- to 1,000-kcal/day deficit and achieve approximately 10% weight loss, while gradually increasing moderate-intensity physical activity to 225 minutes per week.
Prior findings showed that patients assigned to the intervention lost 5.7% of their baseline body weight at 12 months compared with controls.
Invasive disease–free survival was the primary endpoint of the trial; however, the present analysis focused on the mandatory HO-1 substudy, which enrolled the first 542 randomly assigned patients (intervention: n = 272; control: n = 270). Patient-Reported Outcomes Measurement Information System (PROMIS)-29 Profile v2.0 and PROMIS Global Health scores were collected at baseline and at 6 and 24 months. The primary outcome of the substudy—mean physical function—was assessed at 6 months using analysis of covariance (ANCOVA), adjusted for the baseline score, while longitudinal mixed-effects modeling was used to evaluate physical function and other endpoints over time.
Impact on Physical Function
Based on the ANCOVA model at 6 months, patients who were assigned to participate in the weight loss intervention demonstrated a significant improvement in physical function compared with those in the control group (mean between-group difference = 1.9 points; P < .001).
Longitudinal modeling showed that the improvement was maintained through the 2-year intervention period, according to Dr. Ligibel, with significant findings observed at both 6 and 24 months.
Impact on Quality of Life and Symptoms
The investigators also found that, at 6 months, patients enrolled in the weight loss intervention experienced significant improvements in global physical (mean between-group difference = 2.0 points; P < .001) and mental (1.3 points; P = .03) health, social roles and activities (2.3 points; P < .001), and fatigue (−1.7 points; P = .01) compared with the control group. No significant improvements were observed in anxiety, depression, sleep disturbance, or pain interference.
Based on longitudinal modeling analyses, significant improvements in global physical health, global mental health, and social roles and activities were sustained throughout the 2-year intervention period. In contrast, the significant improvement in fatigue observed at 6 months was no longer evident at 24 months.
Experts “Weigh” In
“The [weight loss] intervention was successful in inducing durable improvements in physical function, global physical and mental health, and social functioning,” Dr. Ligibel concluded during the press briefing. She added that the investigators will continue to follow patients to determine whether these benefits may translate into improved invasive disease–free survival and other outcomes.
Marcin Chwistek, MD, FAAHPM, Director of the Supportive Oncology and Palliative Care Program at Fox Chase Cancer Center, Philadelphia, and an ASCO expert in supportive care, commented in the press release: “A program that improves survival and quality of life simultaneously is a program worth delivering.” Echoing that sentiment during the press briefing, Dr. Gralow noted that, even in the absence of survival outcomes data, “the immediate benefits to physical function, fatigue reduction, and quality of life are undeniable.”
Dr. Gralow also emphasized that phone-based coaching reduced geographic and logistical barriers, demonstrating that significant lifestyle changes can be achieved without weekly visits to a specialized clinic. To expand access, she added, “we need to advocate for resources, insurance reimbursement, and accessible programs that allow every breast cancer survivor the opportunity to thrive postdiagnosis.”
Disclosure: The study was funded by National Cancer Institute/National Institutes of Health, with additional support from the Breast Cancer Research Stamp Fund; the Susan G. Komen Breast Cancer Foundation; the Breast Cancer Research Foundation; and the American Cancer Society. For full disclosures of the study authors, visit coi.asco.org.
