Cause-Specific Mortality in Long-Term Survivors of Retinoblastoma

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Abstract
Subsequent malignant neoplasms are a major cause of premature death in survivors of hereditary retinoblastoma. Radiotherapy further increases the risk of death. Mortality information is limited among long-term survivors who were irradiated for hereditary retinoblastoma. We examined cause-specific mortality among 1854 retinoblastoma survivors who were diagnosed from January 1, 1914, through December 31, 1996, at two US institutions. Standardized mortality ratios (SMRs) were calculated by use of US mortality data to estimate expected numbers of deaths. The relative rates (RRs) of mortality due to subsequent malignant neoplasms associated with multiple risk factors were evaluated with Poisson regression models. Cumulative mortality from subsequent malignant neoplasms was calculated by treating other causes of death as competing risks. A total of 151 deaths due to subsequent malignant neoplasms occurred among 1092 hereditary retinoblastoma survivors (SMR = 35, 95% confidence interval [CI] = 30 to 41) compared with 12 deaths among 762 nonhereditary retinoblastoma survivors (SMR = 2.5, 95% CI = 1.3 to 4.4). In this extended follow-up of retinoblastoma survivors, we found no evidence of excess mortality from non-neoplastic causes compared with the general population. However, excess mortality from subsequent malignant neoplasms (particularly sarcomas, melanomas, and cancers of the brain and other parts of the nervous system) among hereditary retinoblastoma survivors extended beyond 40 years after retinoblastoma diagnosis. The additional 13 years of follow-up since our last mortality study revealed a previously unreported increased risk of death due to cancers of the corpus uteri (primarily sarcomas) and confirmed the previously reported elevated risk of death from lung cancer among hereditary retinoblastoma survivors. Among hereditary and nonhereditary retinoblastoma survivors, the relative rates of mortality from subsequent malignant neoplasm were higher in those who had been treated with radiotherapy than in those who had not. Cumulative mortality from subsequent malignant neoplasms at 50 years after retinoblastoma diagnosis was 25.5% (95% CI = 20.8% to 30.2%) for hereditary retinoblastoma survivors and 1.0% (95% CI = 0.2% to 1.8%) for nonhereditary retinoblastoma survivors. The temporal patterns of site-specific excess risks of subsequent malignant neoplasms in retinoblastoma survivors should inform screening programs designed for the early detection and treatment of subsequent malignant neoplasms.