Increased risk of secondary leukemia after single-agent treatment with etoposide for Langerhans' cell histiocytosis

The study evaluated 139 patients diagnosed with Langerhans' cell histiocytosis (LCH) and enrolled in any protocol of the Italian Association of Pediatric Hematology/Oncology since 1982. Treatment was etoposide (VP-16) only in 50 patients, VP-16 and other drugs with an already established leukemogenic effect in 17 patients, only drugs with leukemogenic effect in 6 patients, other drugs in 35 patients, and surgery only in 31 patients. Median length of follow-up after diagnosis was 65 months (range, 1 to 126 months) for a total of 742.5 person-years at risk (PYRs). Three cases of acute myelogenous leukemia (AML) were reported; only 0.0044 case was expected. The standard incidence ratio (SIR) of AML in this cohort was 680.5 [95% confidence interval (CI), 140.2-1988.5], and the incidence rate per 1000 PYRs was 4.0 (95% CI, 0.8-11.8). For the subgroup treated with single-agent VP-16, the SIR after treatment was 2270.0 (95% CI, 275-8199), and the incidence rate after treatment was 14.7 (95% CI, 1.8-42.8). The study confirms a higher risk of leukemia after LCH and supports the hypothesis of an association between treatment-related acute nonlymphocytic leukemia and single-agent treatment with VP-16.