High BMI puts women at greater risk for colorectal neoplasia

Although high body mass index (BMI) has been positively correlated with colorectal cancer, its impact in screening has yet to be fully determined. Now researchers have found a relationship between increasing BMI and risk for significant colorectal neoplasia in women. Our goal was to examine the impact of BMI in a screening population with equal numbers of men and women. Our results may have implications for colorectal cancer screening in female patients. During the study, 2,300 consecutive colonoscopies were performed on asymptomatic patients. Patients were divided into four groups: Patients in group 1 had a BMI<25kg/m2; patients in group 2 had a BMI>25kg/m2 and <30kg/m2; patients in group 3 had a BMI>30kg/m2 and <40kg/m2; and patients in group 4 had a BMI>40kg/m2. Significant colorectal neoplasia was defined as large polyps (>1cm), villous tissue, high-grade dysplasia, more than two polyps and adenocarcinoma. The average age of patients was 57 years; 15 percent had a family history of colorectal cancer.

Doctor and his colleagues found an increased correlation between BMI and risk for colorectal neoplasia for women but not for men. BMI has been shown to be a risk for colon cancer, but we looked at colorectal neoplasia because our quest was to see how it impacted screening. When we screen, we really don’t screen for cancer; we screen for significant colorectal pathology, defined as villous, large tubular adenomas larger than 1 cm, high-grade dysplasia, adenocarcinam and multiple polyps. We found that when we looked at significant neoplasia, there was an increase in (overweight) women but not me. We could not explain the apparent difference in neoplasia risk between overweight men and women. The gender discrepancy is really unclear, he said, but he hypothesized that it may be related to the difference of fat distribution in men and women.

We also questioned whether menopausal status could have influenced the results, though that variable was not considered in the study. I raise the issue of menopause because estrogen may reduce the risk of colorectal polyps and cancer, and estrogen levels decrease with age, though women with higher BMIs tend to retain greater levels of estrogen during and after menopause. In their analysis, also examined the role of diabetes and the use of statin drugs and nonsteroidal anti-inflammatory drugs, none of which were identified as independent risk factors. The findings, suggest that community gastroenterologists may want to consider more aggressive counseling of obese patients about the importance of losing weight and thereby lowering their risk for colorectal cancer.

In view of these finding, gastroenterologists should play a role in discussing weight and its health implications with their patients, especially in light of the increasing rate of obesity. Typically, BMI should constitute a colorectal cancer risk factor for both genders. She added that data on BMI and the risk for colorectal cancer among women have been conflicting, and that closer scrutiny of factors such as hormone replacement therapy among postmenopausal women – which appears to reduce the risk of colorectal cancer – is warranted. The main thing we need to know is why (BMI) matters more for women than for men. If you think the biology of colon polyps progressing to colon cancer is similar in men and women, then why is there this difference between the genders? That’s the key question.