Cancer incidence and mortality among the parents of a population-based series of 2604 children with cancer.

The purpose is to determine cancer incidence and mortality from all causes among parents of children with solid tumors and to formulate hypotheses about heritable risks and associations with parental environmental exposures. A total of 2604 children ages < 15 years included in the Manchester Children's Tumor Registry, 1954-1996, was eligible. Parents of index children were traced and followed up to December 31, 2000, through the United Kingdom National Health Service Central Register. Data on cancer diagnosis and all causes of deaths were obtained. Standardized incidence (SIR) and standardized mortality (SMR) ratios, Ps, and 95% confidence intervals were calculated from serial age and sex-specific cancer incidence and mortality data for England and Wales. There was a significant excess of cancers in parents overall (observed number = 481, expected number = 428.9, SIR = 1.1; P < 0.05) because of central nervous system tumors (SIR = 1.7; P < 0.05), carcinoma breast (SIR = 1.3; P < 0.05), bone and soft tissue sarcoma (SIR = 2.9; P < 0.01), and retinoblastoma (SIR = 62.1; P < 0.001). Diagnoses in the index children associated with excess risk of cancer in their parents were retinoblastoma (SIR = 1.8; P < 0.01) and gonadal germ cell tumors (SIR = 2.3; P < 0.01). There was no excess risk of death from all causes considered together (observed number = 791, expected number = 814.2) nor from any specific cause. These results indicate that there is a small excess of incident cancers among parents of children with solid tumors, probably mainly because of known genes, but mortality is similar to the general population. The study is very reassuring for families of children with cancer.