Long-term Cause-Specific Mortality Among Survivors of Childhood Cancer

Abstract

Survivors of childhood cancer are at increased risk of premature mortality compared with the general population, but little is known about the long-term risks of specific causes of death, particularly beyond 25 years from diagnosis at ages when background mortality in the general population starts to increase substantially. To investigate long-term cause-specific mortality among 5-year survivors of childhood cancer in a large-scale population-based cohort. British Childhood Cancer Survivor Study, a population-based cohort of 17,981 5-year survivors of childhood cancer diagnosed with cancer before age 15 years between 1940 and 1991 in Britain and followed up until the end of 2006. Cause-specific standardized mortality ratios (SMRs) and absolute excess risks (AERs). Overall, 3049 deaths were observed, which was 11 times the number expected (SMR, 10.7; 95% confidence interval [CI], 10.3-11.1). The SMR declined with follow-up but was still 3-fold higher than expected (95% CI, 2.5-3.9) 45 years from diagnosis. The AER for deaths from recurrence declined from 97 extra deaths (95% CI, 92-101) per 10,000 person-years at 5 to 14 years from diagnosis, to 8 extra deaths (95% CI, 3-22) beyond 45 years from diagnosis. In contrast, during the same periods of follow-up, the AER for deaths from second primary cancers and circulatory causes increased from 8 extra deaths (95% CI, 7-10) and 2 extra deaths (95% CI, 2-3) to 58 extra deaths (95% CI, 38-90) and 29 extra deaths (95% CI, 16-56), respectively. Beyond 45 years from diagnosis, recurrence accounted for 7% of the excess number of deaths observed while second primary cancers and circulatory deaths together accounted for 77%. Among a cohort of British survivors of childhood cancer, excess mortality from second primary cancers and circulatory diseases continued to occur beyond 25 years from diagnosis.