Acute myeloid leukemia and myelodysplastic syndrome after adjuvant chemotherapy: A population-based study among older breast cancer patients

BACKGROUND: Chemotherapy for early breast cancer is associated with a small risk of developing myelodysplastic syndrome (MDS) and/or acute myeloid leukemia (AML). The aim of this study was to determine the risk of developing AML or MDS after modern adjuvant chemotherapy in older breast cancer patients and to further define the risk of individual chemotherapy regimens. METHODS: Patients diagnosed with stage I to III breast cancer from 2003 to 2009 were identified in the Surveillance, Epidemiology, and End Results–Medicare and Texas Cancer Registry–Medicare linked databases. The development of AML/MDS, chemotherapy use, and comorbidities were identified with International Classification of Diseases, Ninth Revision and Healthcare Common Procedure Coding System codes. Analyses included descriptive statistics, cumulative incidences, and Cox proportional hazards models to estimate the hazard of AML/MDS after adjustments for clinically relevant covariates. RESULTS: In all, 92,110 patients were included; after a median follow-up of 85 months, the overall rates per 1000 person-years were 0.65 for AML and 1.56 for MDS. Patients who received an anthracycline (A) or anthracycline and taxane (A+T) regimen were more likely to develop AML (hazard ratio [HR] for A, 1.70; 95% confidence interval [CI], 1.16-2.50; HR for A+T, 1.68; 95% CI, 1.22-2.30) or MDS (HR for A, 2.18; 95% CI, 1.70-2.80; HR for A+T, 1.62; 95% CI, 1.29-2.03) than patients who did not receive chemotherapy. Patients using docetaxel and cyclophosphamide (TC) were not at increased risk for AML or MDS. CONCLUSIONS: Adjuvant chemotherapy is associated with a small but significant increase in the risk of AML and MDS, especially with regimens that include A. Longer follow-up is needed to confirm that risk is not increased with the recently adopted TC regimen. Cancer 2018;124:899-906.