Risk of second tumors in survivors of childhood cancer.

A new malignancy was diagnosed in 19 of 414 long-term survivors of cancer in childhood. All but two lesions were attributable to prior radiotherapy; eight were successfully treated. Excluding 4 patients ascertained in connection with the second malignancy, there were 15 in the series who developed a new cancer, in contrast to 0.7 cases expected (p less than 0.001). The 20-year (5-24 years after initial diagnosis) cumulative probability of a second cancer was 12% (S.E. 4%), and the radiation-related cancer rate was 1.8 cases in exposed tissues per million person-years per rad. Host susceptibility may have had an etiologic role, but an oncogenic effect of chemotherapy was not demonstrable. Another 13 study patients developed benign tumors. These findings emphasize the importance of long-term surveillance of children with cancer.