Body size and composition and risk of rectal cancer (Australia)

Although body mass index has been shown to be associated with colon cancer, studies of rectal cancer risk have generally reported no association. The relationship between rectal cancer risk and central adiposity, overall fat mass, and fat-free mass is unknown.

In a prospective cohort study of people aged 27-75 years, body measurements were taken directly; fat mass and fat-free mass being estimated by bioelectrical impedance analysis and central adiposity by waist circumference and waist-to-hip ratio. Among 16,867 men and 24,247 women followed on average for 10.3 years, 229 rectal cancers were ascertained via the population cancer registry.

When comparing the highest tertile with the lowest tertile, weight (hazard ratio = 1.4, 95% confidence interval (CI) 1.1-2.0), waist circumference (hazard ratio = 1.4, 95% CI 1.0-1.9), fat mass (hazard ratio = 1.4, 95% CI 1.0-2.0) and percent fat (hazard ratio = 1.4, 95% CI 1.0-2.0) were positively associated with rectal cancer risk. There was no evidence that risk differed by sex for any of the anthropometric measures.

Waist circumference and fat mass may be weakly related to risk of rectal cancer.