Discordantly High Colorectal Adenoma Prevalence in South Asians

Abstract

Introduction: Colon cancer is the 2nd leading cause of cancer related death in the US. Colonoscopy with polypectomy prevents this. The National Cancer Institute advocates individualized screening strategies to reduce risk and cost. South Asians (Indians, Pakistanis, Bangladeshis, Sri Lankans, Nepalese, etc), the 2nd largest Asian subgroup in USA, are the fastest growing ethnic minority(1). Their CRC incidence is very low (12.3/100,000 compared to 31.6 in Caucasians)(2). However, their colon adenoma prevalence is understudied. Methods: Using ICD-9 code V76.51, 50,206 screening colonoscopy patients between 1/1/06 & 10/31/15 were identified. South Asian category (n=528) was creating using an Asian Indian name database (3). Demographics, BMI, diabetes, race data were extracted. Patient records in our pathology database were reviewed to identify types of polyps detected.Chi square tests examined effect of race on prevalence of adenoma types. Multivariate logistic regression analysis controlled for effect of age, gender, BMI & diabetes. Results: Race distribution was Caucasian 76%, Other (Hispanic, Native American, Pacific Islander) 8.7%, Asian 7 %, Black 7%, South Asian 1%. Majority were female 55%. Means age was 59 yrs & mean BMI was 28.6. South Asian were predominantly male (52%), and had the highest diabetes rate (31%). Overall 27% had tubular adenomas, 7.8 % tubulovillous, 2% villous and 2.2% serrated adenomas, with 9% hyperplastic polyps. Overall males had significantly higher prevalence of all polyps, except sessile serrated. South Asian tubular adenoma prevalence was lower (22%),p < 0.05; but there was no difference with other polyp types. Race was an independent predictor of adenoma presence. Male gender, increasing age & BMI, diabetes were associated with higher prevalence of all polyps except serrated adenomas. Conclusion: South Asians had unexpectedly higher colon adenoma prevalence (22%), despite low rates of colon cancer. Therefore screening strategies for them should not deviate from recommended guidelines at this time, pending further studies of the discordance between their adenoma prevalence and CRC rates. Traditional risk factors for adenomas was not found to affect serrated adenoma prevalence. This needs further study to explain interval cancers, right-sided cancers, etc.