Survival and Recurrence With GLP-1 Receptor Agonists in Breast Cancer
A provocative signal, but not yet an anticancer effect
1. Retrospective EHR-based study; association does not prove causality.
2. High risk of residual confounding despite propensity score matching.
3. Possible healthy-user effect: GLP-1 RA users may have better follow-up, access, adherence, and metabolic care.
4. Strong calendar-time bias: GLP-1 RA use increased in more recent years, when breast cancer care also improved.
5. Weak exposure definition: ≥2 prescriptions do not prove sustained treatment.
6. No time-varying exposure model; immortal-time bias may persist.
7. Landmark analyses reduce bias but do not replace proper time-varying modeling.
8. The signal weakens against the active comparator SGLT2 inhibitors.
9. Insulin/metformin is a problematic comparator because it may represent a sicker diabetes population.
10. Limited tumor biology: ER/HER2 status, grade, nodal burden, tumor size, Ki-67, and genomic risk are inadequately captured.
11. ER-positive rates appear unrealistically low, suggesting incomplete EHR capture.
12. Cancer treatment data appear incomplete; surgery and radiotherapy rates look clinically implausible.
13. RFS is code-based, not a true clinical recurrence endpoint.
14. No breast cancer–specific survival; all-cause mortality may reflect cardiometabolic benefit rather than anticancer effect.
15. No competing-risk analysis despite substantial non-cancer mortality risk.
16. No weight-loss data; the actual metabolic effect is unknown.
17. Effective follow-up is short despite reporting 10-year estimates.
18. Few patients remain at risk beyond 5 years, weakening 10-year KM estimates.
19. High administrative censoring limits late outcome interpretation.
20. Mechanism remains unclear: anticancer effect, weight loss, metabolic control, or patient selection?
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