(ChemotherapyAdvisor) – Myeloid neoplasms arising after radiation therapy differ from those arising postchemotherapy, according to a team of US-based researchers. The conclusion is based on a study entitled “Acute Myeloid Leukemia and Myelodysplastic Syndromes after Radiation Therapy Are Similar to De Novo Disease and Differ From Other Therapy-Related Myeloid Neoplasms,” which was published in the Journal of Clinical Oncology on July 1.

“Therapy-related myeloid neoplasms (t-MN) represent a unique clinical syndrome occurring in patients treated with chemotherapy and/or external-beam radiation (XRT) and are characterized by poorer prognosis compared with de novo disease,” the investigators wrote. This set of clinical outcomes was analyzed in patients who developed acute myeloid leukemia (AML) or myelodysplastic syndromes (MDS) after XRT alone (47 patients) or cytotoxic chemotherapy/combined-modality therapy (C/CMT, 181 patients). These patients were compared with patients with de novo MDS or AML (222 patients). Estimated bone marrow exposure to radiation was determined for each group and the clinical, pathologic, and cytogenetic features and outcome of the XRT group were compared with the C/CMT patients and with patients with de novo MDS and AML.

The investigators reported that patients with t-MN after XRT alone had superior overall survival (P=.006) and lower incidence of high-risk karyotypes (P=.01 for AML and <.001 for MDS) compared with patients in the C/CMT group. In contrast, there were no significant differences in survival or frequency of high-risk karyotypes between the XRT and de novo groups.

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The investigators conclude: “AML and MDS diagnosed in the past decade in patients after receiving XRT alone differ from t-MN occurring after C/CMT and share genetic features and clinical behavior with de novo AML/MDS. Our results suggest that post-XRT MDS/AML may not represent a direct consequence of radiation toxicity and warrant a therapeutic approach similar to de novo disease.”