FAMILIAL AGGREGATION OF TUMORS AND DETECTION OF HEREDITARY NONPOLYPOSIS COLORECTAL-CANCER IN 3-YEAR EXPERIENCE OF 2 POPULATION-BASED COLORECTAL-CANCER REGISTRIES

The clinical data of 2 population-based registries, located in areas w ith different incidence rates of colorectal cancer, were used in order to assess the role of familial factors in the pathogenesis of these t umors. The occurrence of tumors in family members was investigated in 389 subjects with colorectal cancer registered in Modena (Northern Ita ly, an area characterized by a high incidence of colorectal malignanci es) between 1984 and 1986; similar information was obtained in 213 pat ients with tumors of the large bowel registered in Ragusa (Sicily, Sou thern Italy, an area of similar magnitude acid with low incidence rate s for these tumors) in the 3-year period 1988 to 1990. In both series, colorectal cancer occurred significantly more often among relatives o f patients. Controls were patients of the same sex and age (+/- 5 year s) hospitalized during the study periods, but not for gastrointestinal or neoplastic diseases. There were 89 cancer cases (3.1%) among 2,851 relatives of patients in Modena, vs. 17 cases among 1,744 relatives ( 1.0%) in Ragusa (p < 0.01). Apart from colorectal cancer, there was no excess of other types of tumors in patients' families (in both series ). During the 3 years of registration, 17 cases of hereditary non-poly posis colorectal cancer (HNPCC, or Lynch syndrome) were diagnosed in M odena; in contrast, this syndrome was more rare in Ragusa (one case on ly during 3 years of observation). Similarly, many more families with clinical suspicion of HNPCC were recorded in Northern regions (44 vs. 10). Although incidence rates of colorectal cancer are appreciably hig her in Northern than in Southern Italian regions, the excess of this c ancer type among close relatives is similar. However, full-blown HNPCC or suspected Lynch syndrome were significantly more frequent in North ern Italy. (C) 1995 Wiley-Liss, Inc.