ACCURACY OF FAMILY HISTORY OF CANCER OBTAINED THROUGH INTERVIEWS WITHRELATIVES OF PATIENTS WITH CHILDHOOD SARCOMA

The purpose of this study was to determine the accuracy of reporting o f invasive cancer by relatives for family studies. First, we attempted to evaluate whether a lower than expected cancer rate found in second -degree relatives of children with soft-tissue sarcoma was a result of underreporting. Second, we evaluated the accuracy of reported cancer in two data sets by comparing reported cancer information with documen tation by medical records and death certificates. We obtained medical histories from a primary informant, usually the proband's parent, on 3 46 first- and 784 second-degree relatives of 68 childhood and adolesce nt soft-tissue sarcoma patients. To investigate underreporting by the primary informant we conducted an individual interview with each adult relative or proxy. Primary informants reported 22 cancers in first-de gree relatives, all confirmed as invasive cancer, and 71 cancers in se cond-degree relatives with 50 of 67 for which documentation confirmed as invasive. Of 715 individual informants contacted, 15 additional can cers were reported, including 5 confirmed as invasive. The number of f irst-degree relatives with confirmed invasive cancers was within the e xpected range; however, the number of cancers in second-degree relativ es was below the expected range (observed/expected = 0.51 (54/105.5) 9 5% confidence interval (CI) = 0.39-0.67). Thus, the lower than expecte d number of cancers in second-degree relatives was not attributable to underreporting by a single informant or inability to obtain documenta tion. The overreporting of 25 cancers (24.5%) in second-degree relativ es, indicates the need to document all reported cancers. In a second s tudy of 382 childhood and adolescent bone sarcoma families we found th at reports of cancer by one informant for his/her first-degree relativ es were 88% (86/98) accurate. The results suggest that one informant m ay suffice for information on first-degree relatives, but that accurat e reports on second-degree relatives require additional respondents an d documentation.