Breast cancer survivors who experience extreme weight gain have an increased risk of death after breast cancer diagnosis. Moderate weight gain did not affect breast cancer outcomes. These study results were presented at the annual meeting of the American Association for Cancer Research in Orlando, FL.

The investigation, which looked at the association of post-diagnosis weight gain and breast cancer outcomes, was conducted by researchers at Kaiser Permanente in Northern California. Data for the study came from the After Breast Cancer (ABC) Pooling Project, which includes 18,336 breast cancer survivors from four prospective cohorts — three in the United States and one in Shanghai, China.

Participants were diagnosed with invasive primary breast cancer between 1976 and 2006; their ages ranged from 20 to 83 years. Weight and body mass index (BMI) were assessed 18 to 48 months after diagnosis and were compared with each woman’s pre-diagnosis weight.