Aggregation of cancer in first-degree relatives of patients with glioma

Background: Previous studies have been inconclusive in estimating the risk of different cancer sites among close relatives of glioma patients; however, malignant melanoma has consistently been described. Methods: We obtained family history information from 1,476 glioma patients under age 75 years who registered at M. D. Anderson Cancer Center between June 1992 and June 2006. The number of observed cancers (N = 1,001) among 8,746 first-degree relatives (FDR) was compared with the number expected from age-, sex-, and calendar year-specific rates from the Surveillance, Epidemiology, and End Results Program using standardized incidence ratios (SIR). Results: The overall SIR for any cancer was 1.21 (95% confidence interval, 1.14-1.29). Among FDRs under 45 years the overall SIR was 5.08, and for relatives >45 years the overall SIR was 0.95. The SIRs were significantly elevated for brain tumors (2.14), melanoma (2.02), and sarcoma (3.83). We observed an excess of pancreatic cancer, which was significantly higher only among mothers. Conclusion: We observed an overall 21% increase in cancer among the FDRs of glioma patients including excess cases of brain tumors and melanoma, which could point to similar genetic contributions to these two malignancies. A large international linkage study is under way to examine potential genomic regions important for familial glioma.