Unexpected findings on weight loss and breast cancer from international study

Lifestyle

New research in the February 2021 issue of JNCCN—Journal of the National Comprehensive Cancer Network examined body mass index (BMI) data for people with HER2-positive early breast cancer, and found a 5% weight loss in patients over two years in was associated with worse outcomes. Weight gain over the same time period did not affect survival rates.

“The finding that weight loss, and not weight gain, was associated with worse outcomes is unexpected,” said lead researcher Samuel Martel, MD, Universitè de Sherbrooke, Quebec, Canada, who worked with researchers in Belgium, Brazil, Germany, Italy, Switzerland, and the United Kingdom, as well as the National Cancer Institute and the Mayo Clinic in the United States. “We were unable to make a distinction between intentional versus unintentional weight loss, so it’s a matter of speculation whether worse outcomes were due to weight loss, or vice versa. We hope our findings highlight the importance of incorporating consecutive and prolonged data collection on weight in oncology trials, and gaining greater understanding of the metabolic processes after cancer diagnosis that may impact outcomes.”

The BMI data came from the ALTTO BIG 2-06 trial, which collected height and weight data in 8,381 patients with HER2-positive early breast cancer treated with chemotherapy plus trastuzumab and/or lapatinib. 2.2% were underweight at the start of treatment, 45.3% were normal weight, 32.1% were classified as overweight, with another 20.4% obese—defined as a BMI greater than 30. Initial obesity was associated with worse outcomes, including more frequent and serious adverse events leading to treatment discontinuation, as well as significantly worse overall survival rates.

“It was surprising to see that more than 5% weight loss at 2 years was associated with poorer distant disease-free survival. Is our general advice to obese/overweight patient to exercise and lose weight wrong?” questioned Anthony D. Elias, MD, University of Colorado Cancer Center, a member of the NCCN Clinical Practice Guidelines (NCCN Guidelines) Panel for Breast Cancer. “Careful examination of the Kaplan-Meier hazard plots suggests that the relapse curves for those with weight loss are steeper in the second and third years of follow-up, but thereafter are relatively parallel. It’s possible that the weight loss observed early may be an indication for impending relapse of breast cancer.”

The study highlights the importance of weight management in cancer survivorship. The authors hope their findings may provide the basis for further research and oncology trials to guide weight control during the survivorship period.