This analysis, which was based on targeted NGS of peripheral blood cell specimens from 20 patients who developed therapy-related myeloid neoplasms and 44 patients who did not, demonstrated that the prevalence of preexisting CH variants in TP53 at a variant allele frequency of ≥1% was significantly higher at PARPi treatment initiation in peripheral blood cells from patients who ultimately developed therapy-related myeloid neoplasms compared to controls who did not (9 (45.0%) of 20 cases vs. 6 (13.6%) of 44 controls, OR 5.2 (95% CI 1.6–16.0, p = 0.009)). The gene discussed is TP53; the disease is cyclic hematopoiesis.