Background: To examine the incidence, characteristics, and outcomes for second malignancies following the diagnosis of a primary solid tumor in pediatric patients. Methods: The Surveillance, Epidemiology, and End Results (SEER) database was queried from 1973 to 2005, excluding recurrences, in patients <20 y. Results: A total of 31,685 cases of pediatric solid malignancies were identified. Overall, 177 patients were diagnosed with a unique second malignancy before the age 20 (0.56%) The mean follow-up was for 8.5 y (2 mo-30.8 y). Mean age at diagnosis of the primary tumor was 7.7 y. The most common primary malignancies were CNS tumors (22.5%), followed by soft tissue sarcoma (15.8%), retinoblastoma (14.1%), and bone tumors (13%). Hematologic malignancies (35.5%) were the most common second malignancies noted in the cohort, followed by bone tumors (18%) and soft tissue sarcomas (15%). Hematologic malignancies had a shorter latency (3.1 y) compared with solid second tumors (11.6 y). The overall 10-y survival for the entire cohort was 41.5%. For most tumor categories, development of a secondary malignancy was associated with lower 5- and 10-y survival than expected. Conclusions: CNS tumors, retinoblastoma, and soft tissue sarcomas in children are the most common solid primary tumors, with an increased risk of a second malignancy. Leukemia is the most common second malignancy seen in pediatric solid tumors. Second malignancies are associated with significantly reduced survival rates compared with the general childhood cancer population.
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