Clonal Hematopoiesis Dynamics and Evolutionary Fitness During Cancer Treatment Impact Clinical Outcomes

Clonal hematopoiesis (CH) is the age-related expansion of mutated hematopoietic stem cells without other hematologic abnormalities. In patients with solid tumors, CH is associated with higher mortality and may evolve to therapy-related myeloid neoplasms; however, the mechanisms by which cancer treatments promote CH dynamics remain largely unknown. Here, we analyzed 392 serial samples from a prospective cohort of breast cancer patients and showed that cytotoxic treatments (chemotherapy ± radiation) led to strong therapeutic bottlenecks, resulting in significant reductions in hematopoietic allelic populations and differential clonal selection. CH clones that were positively selected and expanded through dose-dependent therapeutic bottlenecks frequently harbored mutations in TP53, PPM1D, SRCAP, DNMT3A, and YLPM1. Patients with positively selected CH during treatment had the shortest progression-free and overall survival compared to patients with unchanging or negatively selected CH across all therapies. These findings, corroborated in independent breast cancer and pan-cancer cohorts, provide strong evidence for clinical relevance of changes in CH during cancer treatment which may help identify patients at high risk for inferior outcomes.