A landmark study published June 2, 2026, in JCO Oncology Practice and simultaneously presented at the 2026 American Society of Clinical Oncology Annual Meeting by researchers at the University of Pennsylvania Perelman School of Medicine has produced findings that could reshape how America's medical community thinks about GLP-1 receptor agonist drugs and how millions of women with obesity approach their own cancer risk.
The study, led by Dr. Elizabeth McDonald, a professor of radiology at Penn and practicing breast radiologist at Penn's Abramson Cancer Center, found that women using GLP-1 medications were approximately 30% less likely to develop breast cancer than women who were not taking these drugs. The finding comes from an analysis of 111,646 women, the largest study of its kind, and the protective effect held even after rigorous statistical matching to control for confounding factors.
