Therapy-related Myelodysplastic Syndrome Following Primary Breast Cancer.

BACKGROUND: Therapy-related myelodysplastic syndrome (t-MDS) is a serious clinical disease occurring after breast cancer treatment. METHODS: A cohort of 11,684 invasive breast cancer (BC) patients from 1990-2014 were followed for incidence of t-MDS through institutional and the Surveillance, Epidemiology and End Results (SEER) Program registries. t-MDS cases were identified using ICD-O SEER registry codes, pathology and chart reports. Treatment, cytogenetics, and time from BC diagnosis to t-MDS and t-MDS diagnosis to last follow up or death were obtained. Incidence rate ratios were calculated using SEER national incidence rates for comparison. RESULTS: 27 cases of t-MDS post BC treatment were confirmed. 96% of cases were breast cancer stage I-II at diagnosis. All patients had received radiation treatment and 59% received adjuvant chemotherapy. Two patients were alive with no evidence of disease after treatment with stem cell transplantation (age 33 and 46). t-MDS incidence was 30 times the expected population rate among patients <55 years (RR 31.8, 95% CI 15.0, 60.8) with shorter time from t-MDS diagnosis to death (median survival time: <55: 8 months, 55-74: 26 months, 75+: 23 months). CONCLUSION: We found elevated t-MDS risk especially among younger BC patients with stem cell transplantation the only observed curative treatment.