2026 ASCO Breast Cancer Highlights: BWEL

Harold Burstein, MD, PhD, and Jennifer A. Ligibel, MD discuss new research from the Breast Cancer Weight Loss (BWEL) trial, as well as recommendations for lifestyle, diet and GLP1 agonists.

October 15, 2026

Dana-Farber

Overview

At the 2026 ASCO Annual Meeting, prespecified secondary outcomes from the BWEL Health Outcomes substudy showed improvements in patient-reported physical function and several symptom and quality-of-life measures with a lifestyle weight-loss intervention compared with health-education control. The trial’s primary endpoint, invasive disease-free survival, remains under follow-up; the supplied material does not report a result for that endpoint.

Background

BWEL (Alliance A011401; NCT02750826) is a phase III trial evaluating a weight-loss intervention in women with overweight or obesity and stage II–III, HER2-negative breast cancer. The study compares a two-year, telephone-based lifestyle intervention with health-education control, with invasive disease-free survival as its primary endpoint. Its Health Outcomes substudy assesses patient-reported outcomes. ASCO’s 2022 guideline reports benefits of exercise and structured lifestyle programs for fitness, strength, fatigue, and quality of life during cancer treatment, while noting limited evidence for effects on recurrence or survival.

Data Highlights

Measure	Reported finding
BWEL enrollment and eligibility	Planned enrollment of 3,180 women with stage II–III, HER2-negative breast cancer and BMI ≥27 kg/m²
Intervention	Two-year, telephone-based lifestyle weight-loss program versus health-education control
Weight change at 12 months	46.5% of intervention participants lost ≥5% of baseline body weight; 22.5% lost ≥10%
2026 Health Outcomes substudy	Intervention improved patient-reported physical function and multiple symptom and quality-of-life measures compared with control
Primary endpoint	Invasive disease-free survival remains under follow-up

Key Findings

BWEL is a phase III study of a two-year telephone-based weight-loss intervention versus health-education control in women with stage II–III, HER2-negative breast cancer and BMI ≥27 kg/m².
The trial’s primary endpoint is invasive disease-free survival, which remains under follow-up in the supplied research context.
At 12 months, 46.5% of participants in the intervention arm had lost at least 5% of baseline body weight, and 22.5% had lost at least 10%.
Prespecified 2026 Health Outcomes substudy results showed better patient-reported physical function and multiple symptom and quality-of-life measures in the intervention group than in the control group.
ASCO’s 2022 guideline reports that randomized trials consistently show benefits of exercise and structured lifestyle programs for cardiorespiratory fitness, strength, fatigue, and quality of life during cancer treatment; evidence for recurrence or survival effects remains limited.
The supplied context notes that NCCN Survivorship Guidelines, Version 3.2026, include physical activity, nutrition, and weight management among survivorship-care counseling topics.

Clinical Implications

The reported BWEL substudy findings concern patient-reported function, symptoms, and quality of life; they do not establish an effect on invasive disease-free survival. ASCO guidance supports discussing exercise and structured lifestyle programs during cancer treatment, while the supplied guideline summary notes that evidence for recurrence or survival effects is limited.

Conclusion

The 2026 BWEL Health Outcomes results report improvements in several patient-reported outcomes with the lifestyle intervention compared with health-education control. The trial’s invasive disease-free survival endpoint remains under follow-up.