Data from Clonal Hematopoiesis in Young Women Treated for Breast Cancer

Abstract

<div>AbstractBackground:<p>Young women treated for breast cancer with cytotoxic therapies are at risk for clonal hematopoiesis of indeterminate potential (CHIP), a condition in which blood cells carrying a somatic mutation associated with hematologic malignancy comprise at least 4% of the total blood system. CHIP has primarily been studied in older patient cohorts with limited clinical phenotyping.</p>Materials and Methods:<p>We performed targeted sequencing on longitudinal blood samples to characterize the clonal hematopoietic landscape of 878 women treated for breast cancer enrolled in the prospective Young Women's Breast Cancer Study.</p>Results:<p>We identified somatic driver mutations in 252 study subjects (28.7%), but only 24 (2.7%) had clones large enough to meet criteria for CHIP. The most commonly mutated genes were <i>DNMT3A</i> and <i>TET2</i>, similar to mutations observed in noncancer cohorts. At 9-year median follow-up, we found no association between the presence of a somatic blood mutation (regardless of clone size) and adverse breast cancer (distant relapse-free survival) or non–breast cancer-related outcomes in this cohort. A subset of paired blood samples obtained over 4 years showed no evidence of mutant clonal expansion, regardless of genotype. Finally, we identified a subset of patients with likely germline mutations in genes known to contribute to inherited cancer risk, such as <i>TP53</i> and <i>ATM</i>.</p>Conclusions:<p>Our data show that for young women with early-stage breast cancer, CHIP is uncommon after cytotoxic exposure, is unlikely to contribute to adverse outcomes over the decade-long follow-up and may not require additional monitoring if discovered incidentally.</p></div>