Epidemiologic studies are conducted to identify life-style and environmental risk factors for cancer and to investigate their interrelationships with genetic determinants of these diseases. Case-control studies of cancers of the bladder, prostate, pancreas, esophagus, stomach, lung, brain, and head and neck, as well as non-Hodgkins lymphoma and multiple myeloma, are in progress. A large case-control study of bladder cancer was completed in Spain to identify occupational bladder carcinogens and to evaluate non-occupational exposures including cigarette smoking (black vs. blond tobacco), phenacetin-containing analgesics, dietary factors, and urination frequency and pH. Genetic susceptibility markers also will be evaluated in relation to bladder cancer risk, as well as their interaction with epidemiologic risk factors. A large multi-center investigation is examining risk factors for malignant neoplasms among subjects being screened for cancers of the prostate, lung, colon, rectum, and ovaries. A large case-control study of bladder cancer in New England is underway to determine the reasons for the persistently elevated bladder cancer mortality and incidence in the northeastern United States. In a case-control study of pancreatic cancer conducted to determine the reasons for the black excess in risk of the disease, established risk factors (mainly cigarette smoking and diabetes mellitus) explained almost the entire black/white disparity in incidence among men. Among women, however, other factors appear to contribute to the racial disparity, notably moderate/heavy alcohol consumption and elevated body mass index. In Sweden, a cohort study indicated that gastroesophageal reflux is strongly associated with risk of esophageal adenocarcinoma, and to a lesser extent, with gastric cardia adenocarcinoma. A study of a Swedish cohort of patients hospitalized for asthma found an moderately increased risk of esophageal or gastric cardia adenocarcinoma among asthmatics, particularly those with gastro-esophageal reflux. In a multicenter, population-based case-control study of esophageal and gastric cancer in the U.S., higher intake of nutrients found primarily in plant-based foods was associated with a reduced risk of adenocarcinomas of the esophagus and gastric cardia, whereas higher intake of nutrients found primarily in foods of animal origin was associated with an increased risk. A case-control study of colorectal adenomas found an increased risk associated with higher intake of red meat, most of which was due to the subgroup of red meat that was cooked until well done/very well done and/or by high-temperature cooking techniques, such as grilling. In Nebraska, results of a population-based case-control study of adenocarcinoma of the esophagus and distal stomach suggested that a diet high in fruit and vegetables, dietary fiber, certain carotenoids, and vitamins may reduce risk esophageal adenocarcinoma and that a diet high in meats and saturated fat may increase risk of distal stomach adenocarcinoma. A population-based case-control study in Shanghai found that, although cigarette smoking and alcohol drinking in general were not risk factors for colorectal cancers, there were small excess risks of rectal cancer among heavy smokers and colon cancer among heavy drinkers. In Sweden and Denmark, a cohort study of acromegaly patients suggested that increased risk of several types of cancer among acromegaly patients may be due to the elevated proliferative and anti-apoptotic activity associated with increased circulating levels of insulin-like growth factor-1 (IGF-1). Pituitary irradiation given to some acromegaly patients may have contributed to the excess risks of brain tumors and thyroid cancer. A case-control study of adult glioma in Nebraska suggested roles for carotenoids and possibly other phytochemicals in reducing risk of adult gliomas, but did not support a role for N-nitroso compounds as a risk factor for gliomas. In a pooled analysis of two population-based case-control studies of non-Hodgkins lymphoma (NHL)in Iowa/Minnesota and Kansas, men with a positive family history of hematolymphoproliferative cancer (HLPC) experienced an increased risk of NHL associated with alcohol, whereas men with no family history of HLPC had no alcohol-related NHL risk. In the case-control study of NHL in Minnesota, cigarette smoking was not clearly associated with t(14;18)-positive NHL. Family history, however, may be a marker for factors that act specifically through t(14;18)-negative pathogenic mechanisms.
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