Background
Previously, eighteen percent of childhood cancer patients who survived five years died within the subsequent 25 years. In recent decades, cancer treatment regimens have been modified with the goal of reducing risk for life-threatening late effects.
Methods
Late mortality was evaluated in 34,033 five-year survivors of childhood cancer (diagnosed <21 years of age from 1970-1999, median follow-up 21 years, range 5-38). Demographic and disease factors associated with mortality due to health-related causes, which exclude recurrence/progression of the original cancer but include deaths that reflect late effects of cancer therapy, were evaluated using cumulative incidence and piecewise exponential models estimating relative rates (RRs) and 95% confidence intervals (CI).
Results
1,618 (41%) of the 3,958 deaths were attributable to health-related causes, including 746 subsequent neoplasm, 241 cardiac, and 137 pulmonary deaths. Reduction in 15-year mortality was observed for all-cause (12.4% to 6.0%, P for trend <0.001) and health-related mortality (3.5% to 2.1%, P for trend <0.001), attributable to reductions in subsequent neoplasm (P<0.001), cardiac (P<0.001) and pulmonary death (P<0.001). Changes in therapy by decade included reduced rates of: cranial radiotherapy for acute lymphoblastic leukemia (1970s 85%, 1980s 51%, 1990s 19%), abdominal radiotherapy for Wilms’ tumor (78%, 53%, 43%), chest radiotherapy for Hodgkin's lymphoma (87%, 79%, 61%), and anthracycline exposure. Reduction in treatment exposure was associated with reduced late mortality among lymphoblastic leukemia and Wilms’ tumor survivors.
Conclusion
The strategy of lowering therapeutic exposure has successfully translated to an observed decline in late mortality among 5-year survivors of childhood cancer.