Therapy-related chronic myelomonocytic leukemia (tCMML) appears to have unique genetics and carries independent prognostic impact, according to a study involving nearly 500 individuals. Moreover, tCMML has few of the characteristics commonly seen with therapy-related myelodysplastic syndrome/acute myeloid leukemia (t-MDS/AML). Investigators looked at the independent prognostic impact of t-CMML, which was diagnosed in 9% of patients ~7 years after chemotherapy and/or radiation therapy. Among the results:

• Compared to those with newly-diagnosed CMML, t-CMML patients had higher LDH levels, higher frequency of karyotypic abnormalities, and higher risk cytogenetic stratification.
• There were no differences in the distribution of gene mutations.
• Unlike with t-MDS/AML, balanced chromosomal translocations, abnormalities of chromosome 11q23, and Tp53 mutations were rare.
• Median overall survival was ~11 months for patients with t-CMML, vs 26 months for those with dysplastic-CMML.
• Leukemia-free survival was 50 and 127 months, respectively.
• The prognostic impact remained in the context of the Mayo Molecular Model and the GFM prognostic model.