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Purpose. We recently reported an association of adult BMI change with colon cancer risk. Here, we sought to further explore this association with respect to postmenopausal HRT use in a larger study population. Methods. We included 1,457 postmenopausal women participating in an ongoing population-based case-control study of colon cancer. Results. We confirmed a previously reported association of adulthood weight gain and increased risk of colon cancer: compared to those with <5 kg/m2 change of BMI, women who reported moderate (5-10 kg/m2) and large (>10 kg/m2) BMI changes since their 20s had OR estimates of 1.54 (95% CI = 1.09-2.19) and 1.45 (95% CI = 0.90-2.33), respectively (P for trend = 0.05). Stratified analyses showed that this association was limited to HRT nonusers: ORs were 1.77 (95% CI = 1.02-3.05) and 2.21 (95% CI = 1.09-4.45), respectively (P for trend = 0.03), for BMI changes occurring between the 20s decade and time of recruitment among non-users. Similar associations were observed for BMI changes since the 30s decade. There was no association among HRT users. Conclusion. Our results suggest early adulthood weight gain increases colon cancer risk in postmenopausal women who do not use HRT. [ABSTRACT FROM AUTHOR]

Obesity has been associated with increased colon cancer risk in epidemiological studies; however, the specific time periods during which obesity may be most relevant as well as how changes in adult body size over time affect colon cancer risk have not been well explored. We evaluated potential associations between BMI in each age decade(20s, 30s, 40s, 50s, and 2 years before study recruitment ("recruitment period")) and in BMI changes over timeand colon cancer risk in a population-based case-control study comprising 438 cases and 491 controls. We found that obese (BMI>or=30.0 kg/m2) compared to normal (BMI>or=18.5 to <25.0 kg/m2) body size at the recruitment period was associated with increased colon cancer risk (odds ratio (OR)=1.54; 95% confidence interval (CI)=1.03-2.31; P=0.03). No associations were observed for obese body size in the other age decades. An increased risk was found for changes in BMI between the 30s decade and the recruitment period of 5-10 kg/m2 (OR=1.54; 95%CI=1.02-2.34; P=0.04) and >10 kg/m2 (OR=2.40; 95% CI=1.23-4.66; P=0.01) (P trend=0.01). Stratification by gender revealed that BMI changes>10 kg/m2 increased risk in women but not men. Similar results were found for BMI changes between the 20s decade and the recruitment period but effect sizes were smaller. Our results provide additional support to obesity's role in colon cancer and suggest large body size increases exceeding 10 kg/m2 may potentially be more important after age 30, particularly among women; however, prospective studies with sex hormone, growth factor, and pro-inflammatory biomarkers are needed to provide insights to the underlying biological mechanism(s).

Three recent studies identified common variants on 8q24 that confer modestly increased susceptibility to colorectal cancer. Here, we replicate the association in a population-based case-control study of colon cancer, including 561 cases and 721 unrelated controls. The rs6983267 marker was significantly associated with colon cancer risk. Compared with those homozygous for the T allele, the heterozygous and homozygous carriers for the G allele had an age-adjusted odds ratio of 1.39 (95% confidence interval, 1.03-1.88) and 1.68 (95% confidence interval, 1.21-2.33), respectively. An additive model showed strong evidence for a gene-dose response relationship (P(trend) = 0.0022). The association remained statistically significant when restricted to Caucasians only (527 cases and 679 controls; P(trend) = 0.0056). Further adjustment for other known risk factors did not alter the results. Stratified analysis revealed no evidence for effect modification by family history of colorectal cancer, age, or gender. These data replicate the association identified from recent studies, providing additional evidence supporting the rs6983267 genetic polymorphism as a marker predisposing to colon cancer.