Comparative Study of Risk Factors for Sessile Serrated Adenomas and Tubular Adenomas

Introduction: Colorectal cancer (CRC) is the 2nd leading cause of cancer-related mortality in the USA. While adenomatous polyps are the predominant precursors for CRC, sessile serrated adenomas (SSA) may contribute to up to 1/3 of all CRC, especially right-sided CRC and interval CRC. Risk factors for conventional adenomas are well studied, but not for SSAs, especially with respect to race and gender. Our goal was to identify and compare risk factors for SSA and tubular adenomas (TA). Methods: Using ICD-9 code, all screening colonoscopies between 1/1/06 and 10/31/15 at our institution were identified. The subset with polyps, specifically SSA and TA were then identified. Patients without any polyps formed the reference group. Race and ethnicity were identified by chart review. American Indians, Pacific Islanders, Hawaiians were grouped into “other” race category due to very few such patients. “Unknown” group included those without identifiable race or ethnicity. Age (categorized as 50-60, 60-70, 70-85), sex, BMI, DM, smoking (ever/never) and alcohol intake (light/moderate/heavy) data were extracted by chart review. Chi square test was used to examine effect of individual variables on SSA and TA risk, followed by multivariate regression analysis. Results: Study population demography is detailed in Table 2. For tubular adenomas, male sex, OR 1.58, higher BMI, OR 1.008, diabetes, OR 1.15, and increasing age (OR 1.52; 95% CI 1.35-1.71), were associated with higher risk. For SSAs, female sex, OR 1.21, non-diabetic state, OR 1.46, excess alcohol consumption, OR 2.61, nonsmoking status, OR 1.35, were associated with higher risk. Blacks were at lower risk for SSA compared to Whites, OR 0.24 (0.16-0.37). BMI and age were not significant risk factors for SSA, and younger age group was at a slightly higher risk compared to older individuals. There was a higher odds of SSA detection if the colonoscopy was performed more recently, specifically after 2010, OR 1.65 (1.59-1.71).Table: Table. Study Population CharacteristicsTable: Table. Odds Ratios with 95% Wald Confidence Limits for Sessile Serrated Adenomas (SSA) and Tubular Adenomas (TA)Figure: Odds Ratios with 95% Wald Confidence Limits for Sessile Serrated Adenomas.Figure: Odds Ratios with 95% Wald Confidence Limits for Tubular Adenomas.Conclusion: In the largest SSA study to date, we found a unique risk profile for SSA, wherein females, Caucasians, non-diabetics, and nonsmokers, were found to have a significantly higher risk. Higher alcohol consumption was the only conventional risk factor for CRC that also applied to SSA. Neither age, nor obesity increased SSA risk. The pathophysiology of this SSA risk profile needs further study, which could lead to risk reduction interventions.For now, the endoscopist needs to meticulously examine the proximal colons of such individuals.