Adenoma to Colorectal Cancer Estimated Transition Rates Stratified by BMI Categories-A Cross-Sectional Analysis of Asymptomatic Individuals from Screening Colonoscopy Program

Abstract

Most colorectal cancers (CRC) assumedly develop from precursor lesions, i.e., colorectal adenomas (adenoma-carcinoma sequence). Epidemiological and clinical data supporting this hypothesis are limited. Therefore, the aim of the present study is to estimate relative dynamics of colorectal adenoma-carcinoma sequence for groups of screenees stratified by BMI (body mass index) based on prevalence data from Polish Colonoscopy Screening Program (PCSP). We performed a cross-sectional analysis of database records of individuals who entered the national opportunistic colonoscopy screening program for CRC in Poland. We calculated prevalence of adenomas and CRCs adjusted for sex, 5-year age group, family history of CRC, smoking, diabetes and use of aspirin, hormonal therapy and proton-pump inhibitors use. Thereafter we calculated estimated transition rate (eTR) with confidence intervals (CIs) defined as adjusted prevalence of more advanced lesion divided by adjusted prevalence of less advanced lesion. All analyzes were stratified according to the BMI categories: normal (BMI 18.0 to <25.0), overweight (BMI 25.0 to <30.0) and obese (BMI ≥ 30.0). Results are reported in the same respective order. After exclusions we performed analyses on 147,385 individuals. We found that prevalence of non-advanced adenomas is increasing with BMI category (12.19%, 13.81%, 14.70%, respectively; p < 0.001). Prevalence of advanced adenomas was increasing with BMI category (5.20%, 5.77%, 6.61%, respectively; p < 0.001). Early CRCs prevalence was the highest for obese individuals (0.55%) and the lowest for overweight individuals (0.44%) with borderline significance (p = 0.055). For advanced CRC we found that prevalence seems to be inversely related to BMI category, however no statistically significant differences were observed (0.35%, 0.31%, 0.28%; p = 0.274). eTR for non-advanced adenoma to advanced adenoma is higher for obese individuals than for overweight individuals with bordering CIs (42.65% vs. 41.81% vs. 44.95%) eTR for advanced adenoma to early CRC is highest for normal individuals, however CIs are overlapping with remaining BMI categories (9.02% vs. 7.67% vs. 8.39%). eTR for early CRC to advanced CRC is lower for obese individuals in comparison to both normal and overweight individuals with marginally overlapping CIs (73.73% vs. 69.90% vs. 50.54%). Obese individuals are more likely to develop adenomas, advanced adenomas and early CRC but less likely to progress to advanced CRC. Therefore, this study provides new evidence that obesity paradox exists for colorectal cancer.

Keywords: colonoscopy; colorectal adenoma; colorectal cancer; colorectal cancer epidemiology; colorectal cancer prevalence; screening.

Figure 1

Comparison of adjusted prevalence: (A): adjusted prevalence of non-advanced adenoma stratified by BMI categories; (B): adjusted prevalence of advanced adenoma stratified by BMI categories; (C): adjusted prevalence of early CRC stratified by BMI categories; (D) adjusted prevalence of advanced CRC stratified by BMI categories. Error bars represent 95% confidence interval.

Figure 2

Comparison of eTRs stratified by BMI: (A)—non-advanced adenoma to advanced adenoma eTR (eTR_nAA→AA); (B)—advanced adenoma to early CRC (eTR_AA→eCRC); (C)—early CRC to advanced CRC eTR_eCRC→aCRC). Error bars represent 95% confidence interval. BMI is a categorical variable—dotted lines are for visual purposes only. Note that y-axis is zoomed in.

Figure 3

Prevalence ratios for BMI category and types of lesions. nAA—non-advanced adenoma, AA-advanced adenoma, eCRC—early CRC, aCRC—advanced CRC.