Second solid malignancies among children, adolescents, and young adults diagnosed with malignant bone tumors after 1976: follow-up of a Children's Oncology Group cohort.

BACKGROUND: 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).
METHODS: 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).
RESULTS: 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%).
CONCLUSIONS: 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.