Temporal Trends of Subsequent CNS Malignancies Among Survivors of Childhood Cancer

PURPOSE It is not known whether temporal changes in childhood cancer therapy have reduced risk of subsequent malignant neoplasms (SMNs) of the central nervous system (CNS), a frequently fatal late effect of cancer therapy. METHODS Five-year survivors of primary childhood cancers diagnosed between 1970-1999 in the Childhood Cancer Survivor Study with a subsequent CNS SMN were identified. Cumulative incidence rates and standardized incidence ratios (SIR) were compared among survivors diagnosed between 1970-1979 (N = 6223), 1980-1989 (N = 9680), and 1990–1999 (N = 8999). Multivariable models assessed risk factors for CNS SMN. RESULTS 157 CNS SMNs (1970s, 52; 1980s, 63; 1990s, 42) were identified, excluding meningiomas, which were most often malignant gliomas. The proportion of survivors receiving any cranial radiotherapy (CRT) exposure was reduced over time (1970s 77.0%, 1980s 54.3%, 1990s 33.9%), while the proportion receiving >35Gy CRT showed a smaller reduction (11.4%, 10.8%, and 8.5%, respectively). Twenty-year cumulative incidence (95% CI) and SIR (95% CI) for CNS SMN by treatment decade were 0.32% (0.18-0.46%) and 6.6 (5.0–8.7); 0.55% (0.41-0.70%) and 8.3 (6.6-10.4); and 0.43% (0.31-0.55%) and 9.2 (7.0–12.0), respectively, with no statistically significant decreases between eras. Multivariable analyses showed increased risk for CRT dose levels >10Gy and for primary diagnoses of medulloblastoma/PNET (HR 18.7, 9.2-37.9) and astrocytoma (HR 10.1, 5.3-19.5). Three-year cumulative incidence of death after CNS SMN, by treatment decade, were 76%, 74%, and 73%, respectively. CONCLUSION CNS SMN incidence has not decreased despite fewer survivors exposed to CNS-directed radiotherapy. CNS SMNs remain a substantial source of mortality for affected patients.