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Cancer is the second-leading cause of death in the United States. The lifetime probability of a women being diagnosed with an invasive cancer is 38%.1 Up to 20% of all cancers might be caused by excessive weight (overweight or obesity).2 The burden of obesity on society continues to rise and warrants closer attention by clinicians for both cancer prevention and improved outcomes after diagnosis. The general focus of this chapter is the association of obesity with nongynecologic cancer in women. The mechanisms by which body weight influences the development of cancer are discussed. Particular emphasis is placed on the impact of increased body weight on prognosis, survival, and risk of recurrence. In addition, prevention and management strategies are discussed to aid clinicians in counseling patients regarding obesity-related cancers.
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PREVALENCE AND EPIDEMIOLOGY
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Surveillance, Epidemiology, and End Results (SEER) data estimates as of 2007 suggest that there will be 50,000 new cases of cancer yearly in women (7%) that are attributable to obesity.2 More than one-third of US adults are obese (approximately 78.6 million), another third are overweight,3 and the prevalence is increasing. The percentage of cancer cases attributable to obesity varies widely for different cancer types but is as high as 40% for some cancers, particularly adenocarcinomas of the endometrium and esophagus. A projection of the future health and economic burden of obesity in 2030 estimated that continuation of existing trends in obesity will lead to about 500,000 additional cases of cancer in the United States by 2030 (Table 12–1).4
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A systematic review and meta-analysis were performed in 2008 to assess the strength of associations between body mass index (BMI; defined as weight in kilograms divided by height in square meters) and different sites of cancer and to investigate differences in these associations between sex and ethnic groups.5 In women, strong associations were noted between a 5-kg/m2 increase in BMI and endometrial (relative risk [RR] 1.59, confidence interval [CI] 1.5–1.68), gallbladder (RR 1.59, CI 1.02–2.47), and renal (RR 1.34, CI 1.25–1.43) cancers and esophageal adenocarcinoma (RR 1.51, CI 1.31–1.74). A weaker positive association (RR < 1.20) was observed between increased BMI and postmenopausal (PMP) breast, pancreatic, thyroid, and ...