ABSTRACT
PURPOSE: Anthracycline-associated risk for subsequent breast cancer in childhood cancer survivors is hypothesized to be mediated by TP53 mutation-related gene-environment interactions. We characterized treatment/genetic risks and the impact of screening for breast cancer in the St Jude Lifetime Cohort. PATIENTS AND METHODS: Female participants underwent risk-based assessments, prior health event validation, chest radiation dosimetry, and whole genome sequencing. Breast biopsy reports were reviewed. A subgroup (n = 139) underwent both breast magnetic resonance imaging and mammography. Multivariable regression was used to calculate hazard ratios (HRs) and 95% CIs. RESULTS: Among 1,467 women, 56 developed 68 breast cancers at a median age 38.6 (range, 24.5 to 53.0) years. Cumulative incidences at age 35 years were 1% (no chest radiation) and 8% (≥ 10 Gy of chest radiation). In adjusted models, breast cancer was associated with 20 Gy or more of chest radiation versus none (HR, 7.6; 95% CI, 2.9 to 20.4), anthracycline exposure versus none (1 to 249 mg/m2: HR, 2.6; 95% CI, 1.1 to 6.2; ≥ 250 mg/m2: HR, 13.4, 95% CI, 5.5 to 32.5), and having a breast cancer predisposition gene mutation (HR, 23.0; 95% CI, 7.3 to 72.2). Anthracyclines 250 mg/m2 or greater remained significantly associated with increased risk of breast cancer in models excluding survivors with cancer predisposition gene mutations, chest radiation 10 Gy or greater, or both. Sensitivity/specificity were 53.8%/96.3% for mammography, 69.2%/91.4% for magnetic resonance imaging, and 85.8%/99.7% for dual imaging. Breast cancers detected by imaging and/or prophylactic mastectomy compared with physical findings were more likely to be in situ carcinomas, smaller, without lymph node involvement, and treated without chemotherapy. CONCLUSION: Higher doses of anthracyclines are associated with increased risk of breast cancer independent of mutations in known cancer predisposition genes. Surveillance imaging identifies breast cancers less likely to require chemotherapy than those detected by physical findings.
