Familial carcinoid tumors and subsequent cancers: a nation-wide epidemiologic study from Sweden.

Carcinoids are rare neuroendocrine tumors, mainly located in the bowel, stomach and lung. Familial risks in carcinoid tumours are not well known apart from multiple endocrine neoplasia 1 (MEN1). We used the nation-wide Swedish Family-Cancer Database on 10.1 million individuals for assessment. Carcinoid tumors were retrieved from the Cancer Registry covering the years 1958-1998. The offspring generation, aged 0-66 years, accumulated 190 million person-years at risk. The age-adjusted incidence rates were 0.76 for men and 1.29/100,000 for women. Standardized incidence ratios (SIRs) were calculated for offspring when their parents had a carcinoid or any other cancer. When parents presented with carcinoids, SIRs for offspring were 4.35 (n = 8, 95% CI 1.86-7.89) for small intestinal and 4.65 (n = 4, 95% CI 1.21-10.32) for colon carcinoids. If both offspring and parents presented with small intestinal carcinoids, the SIR was 12.31 (n = 4, 95% CI 3.20-27.34). Offspring carcinoids were also increased if parents presented with bladder and endocrine gland tumors, the latter association probably partially due to MEN1. Risks for second cancers were increased, particularly at sites where familial risks were found, including carcinoids in the small intestine.