The Penn Medicine retrospective cohort of 111,646 women (ages 45-80, BMI ≥25) found GLP-1 users had 30.5-35.1% lower breast cancer odds versus non-users, with one-to-one matching on age, race, BMI, density and diabetes to reduce confounding. This observational design (not RCT) cannot establish causality and omitted GLP-1 duration, specific agents like semaglutide, BRCA status or tumor subtypes. Weight-loss mechanisms likely contribute via reduced postmenopausal estrogen and lowered systemic inflammation, yet the study under-explored whether benefits persist independent of BMI drop. Related evidence from the SELECT trial (semaglutide, n=17,604; NEJM 2023) showed cardiovascular gains partly via anti-inflammatory pathways that may overlap with oncogenesis; a 2024 Diabetes Care analysis (n=1.2M) similarly linked GLP-1s to lower obesity-related cancers but flagged detection bias. Missed in original coverage: potential surveillance bias among medicated patients and lack of genetic stratification. Pending RCTs in high-risk cohorts will clarify if these drugs become true preventives beyond lifestyle advice.