Obesity and Colorectal Cancer
There is strong evidence that modifiable lifestyle factors such as obesity play a key role in colorectal carcinogenesis. Epidemiologic data have consistently reported a positive association between obesity and colorectal cancer. The relative risk associat
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Abstract
There is strong evidence that modifiable lifestyle factors such as obesity play a key role in colorectal carcinogenesis. Epidemiologic data have consistently reported a positive association between obesity and colorectal cancer. The relative risk associated with general obesity (as assessed by BMI) is higher in men than in women and for cancer of the colon than for cancer of the rectum. Abdominal obesity (as assessed by waist circumference (WC) or waist-to-hip ratio) is associated with an increased risk of colorectal cancer in both sexes, with stronger associations for cancer of the colon than for cancer of the rectum. Plausible biological mechanisms include insulin resistance, hyperinsulinemia, chronic inflammation, altered levels of growth factors, adipocytokines and steroid hormones. In addition to its effect on colorectal cancer incidence, obesity may play a role in colorectal cancer recurrence, treatment outcomes and survival. Understanding the effects of childhood and adolescent obesity and weight change over the life course in relation to future risk of colorectal cancer is incomplete but essential for targeted preventive recommendations. This chapter summarizes the current evidence on the relationship between obesity and colorectal cancer and colorectal adenoma, a common precursor lesion. Keywords
Obesity
Colorectal cancer Epidemiology
C. Jochem M. Leitzmann (&) Department of Epidemiology and Preventive Medicine, University of Regensburg, Regensburg, Germany e-mail: [email protected] © Springer International Publishing Switzerland 2016 T. Pischon and K. Nimptsch (eds.), Obesity and Cancer, Recent Results in Cancer Research 208, DOI 10.1007/978-3-319-42542-9_2
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C. Jochem and M. Leitzmann
Introduction
Worldwide, colorectal cancer is the third1 most common cancer in men and the second2 leading malignancy in women, accounting for 10.0 and 9.2 % of all cancer cases, respectively [1]. In 2012, approximately 746,000 new colorectal cancer cases were diagnosed in men and 614,000 were diagnosed in women [1]. Age-standardized incidence rates (ASRs) vary widely across the world, and almost 55 % of all cases occur in economically more developed regions such as Australia/New Zealand (men: 44.8 per 100,000, women: 32.2), Europe (men: 37.3, women: 23.6) and Northern America (men: 30.1, women: 22.7) [1]. Incidence rates are lowest in economically less developed regions such as Africa (men: 7.0, women: 5.8) and South Central Asia (men: 7.0, women: 5.2) [1]. Colorectal cancer is the fourth3 most common cause of death from cancer, contributing to 8.5 % of total cancer mortality worldwide (694,000 deaths per year in both sexes) [1]. Overall, colorectal cancer is among those cancers that contribute most to the global burden of cancer—in terms of incidence, mortality and disability-adjusted life years (DALYs) [2]. Higher rates of colorectal cancer in “westernized” countries suggest that environmental or lifestyle factors may play a key role in the etiology of colorectal can
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