Treatment-Induced Acute Leukaemia after Major Response to Cyclophosphamide-Based Metronomic Chemotherapy in Refractory Heavily Pre-Treated Prostate Cancer

Background: Metronomic chemotherapy is based on antiangiogenic and immunologic mechanisms obtained by the administration of traditional cytotoxic drugs at lower concentration without rest periods. The low dosage induces fewer or no side effect compared to classic maximum tolerated dose administration (MTD). At present, no treatment related acute leukaemia was reported in cyclophosphamide-based metronomic chemotherapy (CMC). Case: We report the case of an 81-year-old man considered as having castration and chemo-refractory metastatic prostate cancer. CMC was started. Objective response was observed in this heavily pre-treated patient with progression free survival lasting more than 30 months. No toxicity was observed in this period and his autonomy was maintained. Finally, our patient developed a chemotherapy-induced acute myeloid leukaemia at 36th month of CMC. Conclusion: Even CMC is a well-tolerated treatment; secondary acute leukaemia is related to cumulative dose of cyclophosphamide. The benefit and the risk of long-term exposure to cyclophosphamide should be carefully balanced.