The growing number of individuals surviving childhood cancer has increased the awareness of adverse long‐term sequelae. One of the most worrisome complications after cancer therapy is the development of second malignant neoplasms (SMNs).

The authors describe the incidence of solid organ SMN in survivors of pediatric malignant bone tumors who were treated on legacy Children's Cancer Group/Pediatric Oncology Group protocols from 1976 to 2005. This retrospective cohort study included 2842 patients: 1686 who were treated for osteosarcoma (OS) and 1156 who were treated for Ewing sarcoma (ES).

The cohort included 56% boys/young men and 44% girls/young women, and the median age at primary diagnosis was 13 years. The median length of follow‐up was 6.1 years (range, 0‐20.9 years). In this analysis, 64% of patients were alive. Seventeen patients with solid organ SMN were identified. The standardized incidence ratio was 2.9 (95% confidence interval [CI], 1.4‐5.4) for patients who were treated for OS and 5.0 (95% CI, 2.6‐9.4) for patients who were treated for ES. The median time from diagnosis to development of solid SMN was 7 years (range, 1‐13 years). The 10‐year cumulative incidence of solid organ SMN for the entire cohort was 1.4% (95%CI 0.6%‐2%).

The magnitude of risk of solid SMNs was modest after treatment for malignant bone tumors. However, radiation‐related solid SMNs will increase with longer follow‐up. Because nearly 33% of patients die from their disease, recurrence remains the most significant problem. The development of improved therapies with fewer long‐term consequences is paramount. Follow‐up should focus on monitoring for both recurrence of primary malignancies and development of SMNs. Cancer 2008. © 2008 American Cancer Society.