Associations between small intestine cancer and other primary cancers: An international population‐based study

Abstract

Cancer of the small intestine is a rare neoplasm, and its etiology remains poorly understood. Analysis of other primary cancers in individuals with small intestine cancer may help elucidate the causes of this neoplasm and the underlying mechanisms. We included 10,946 cases of first primary small intestine cancer from 13 cancer registries in a pooled analysis. The observed numbers of 44 types of second primary cancer were compared to the expected numbers derived from the age-, gender-and calendar period-specific cancer incidence rates in each registry. We also calculated the standardized incidence ratios (SIR) for small intestine cancer as a second primary after other cancers. There was a 68% overall increase in the risk of a new primary cancer after small intestine carcinoma (SIR 5 1.68, 95% confidence interval [CI] 5 1.47-1.71), that remained constant over time. The overall SIR was 1.18 (95% CI 5 1.05-1.32) after carcinoid, 1.29 (1.01-1.63) after sarcoma, and 1.27 (0.78-1.94) after lymphoma. Significant (p < 0.05) increases were observed for cancers of the oropharynx, colon, rectum, ampulla of Vater, pancreas, corpus uteri, ovary, prostate, kidney, thyroid gland, skin and soft tissue sarcomas. Small intestine cancer as a second primary was increased significantly after all these cancers, except after oropharyngeal and kidney cancers. Although some of the excess may be attributable to overdiagnosis, it is plausible that most additional cases of second primary cancers were clinically relevant and were due to common genetic (e.g., defects in mismatch or other DNA repair pathways) and environmental (e.g., dietary) factors. ' 2005 Wiley-Liss, Inc.Key words: small intestine cancer; second primary cancers; registrybased study Cancer of the small intestine is a rare neoplasm, with an estimated incidence of less than 1/100,000 in most countries, 1 although this may be increasing. 2 The rarity of this malignancy is all the more noteworthy in that the small intestine is situated between the stomach and colon, which are common sites of cancer, and that it constitutes 75% of the length of the alimentary tract and 90% of its mucosal surface area. The 5-year relative survival was 37% among patients diagnosed with small intestine cancer in the period 1990-94 in 22 European countries. 3 Little is known about the etiology of this cancer. Several studies have reported higher risks following Crohn's disease, celiac disease and familial adenomatous polyposis (FAP). 4 Results on tobacco smoking are conflicting: although 2 studies did not report any association, 5,6 2 other studies showed an increased risk of small intestine cancer among smokers. 7,8 Studies of second primary cancers have reported associations with cancers of colon, rectum, and endocrine glands as well as skin melanoma. 9-13 The results, however, were often based on few cases and cannot be considered conclusive.We report the results of a pooled analysis of data from 13 population-based cancer registries on second primary cancers in small intestine cancer patients, wi...

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