Clonal hematopoiesis in metastatic urothelial and renal cell carcinoma.

Clonal hematopoiesis (CH) is an age-related expansion of white blood cell (WBC) progenitors linked to risk of hematological malignancy. Patients with cancer have increased CH prevalence compared to healthy populations, but the characteristics and relevance of CH in advanced urological cancers are unknown. We interrogated CH and circulating tumor DNA (ctDNA) in 299 patients with metastatic urothelial or renal cell carcinoma using error-corrected targeted sequencing of matched WBC DNA and plasma cell-free DNA (cfDNA). 73% of patients carried CH variants at ≥0.25% allele frequency, with 13% exhibiting large CH populations marked by variants ≥10%. CH presence, clone size, and genotype did not impact patient survival. However, CH variants frequently affected solid cancer driver genes and were not individually discriminable from ctDNA variants based on cfDNA features including fragment length. In contrast, matched WBC DNA sequencing to ≥25% of cfDNA depth sufficiently resolved CH from ctDNA variants. Serial profiling revealed ctDNA and CH temporal dynamics including treatment-related expansion of PPM1D-mutated CH clones following platinum chemotherapy. Our data reveal the molecular landscape of CH in urological cancers and suggest that CH interferes in clinical ctDNA genotyping. We urge test providers to comprehensively filter CH from ctDNA results using matched WBC sequencing and propose a cost-effective framework for its integration into existing plasma-only assays.