Multiple primary neoplasms in childhood: data from the German Children's Cancer Registry.

The German Children's Cancer Registry (GCCR) has documented all malignancies during the first 15 years of life in Germany since 1980. In a series of 20,388 cancer cases to the end of 1995, 127 children with multiple primary neoplasms up to the age of 15 years were identified. The children were monitored for 82,591 person-years with a mean observation time of 4.1 years. Relative and cumulative risk for the occurrence of second malignant neoplasms were estimated only for the first 15 years of life, as follow-up data beyond childhood are incomplete and valid data on the incidence of cancer in adolescents and adults are not available in Germany. The overall standardised incidence ratio for a second malignancy was 12.5 (95% CI: 10.4-14.9) which implies an absolute excess risk of 141.5 per 10(5). The estimated cumulative risk within 10 years after the first malignancy was 1.9% (95% CI: 1.5-2.3). It is expected that the risk will alter with prolongation of follow-up beyond childhood.