Enhancing endocrine therapy activity via fasting cycles: biological rationale and clinical feasibility.

We found that periodic fasting increases the anti-cancer activity of endocrine agents used to treat hormone receptor-positive breast cancer and delays acquired resistance to them by reducing blood leptin, insulin and insulin-like growth factor 1 (IGF1). Our work supports further clinical studies of fasting as an adjuvant to endocrine agents in breast cancer patients.