Study On Prevalence Of Colorectal Neoplasms And Optimal Beginning Age Of Screening Among Individuals At Average Risk For Colorectal Cancer

Incidence rates for colorectal cancer in China is rising year by year. Most of thecolorectal cancer are developed from asymptomatic average-risk population. Screening ofcolorectal cancer can detect early cancer and precancerosis, and can make patients betreated in time. Thus it can effectively reduce colorectal cancer incidence and mortality.Average-risk population means persons who have no colorectal cancer associatedsymptoms or warning signs, no colorectal cancer and colorectal adenomatous polyp historyand family history, no hereditary colorectal cancer and inflammatory bowel disease history.For the average risk crowd, foreign screening guidelines recommend that colorectal cancerscreening start from50years. However, incidence rates for colorectal cancer are differentamong different races. Whether foreign screening guidelines are suitable to our countrycrowd still needs to be studied. So far, our country still has no colorectal cancer screeningguidelines in asymptomatic average risk crowd. So, based on the prediction rule foradvanced colorectal neoplasm in average-risk population, this study aimed to analyze thedistribution features of the advanced colorectal neoplasm in average-risk population andevaluate the prevalence of advanced colorectal neoplasm in different risk crowd and agegroups. Consequently, we can provide the scientific basis to determine the optimal startingage for colorectal cancer screening.Materials and MethodsWe used the self-made questionnaire to conduct a survey on average-risk adults whocame to the19nationwide representative hospitals and underwent a total colonoscopy. Theprevalence and distributions of colorectal neoplasm in average-risk population wereanalysed by using the chi-square test for categorical variables and the unpaired t test forcontinuous variables. We evaluated the occurrence risk of advanced colorectal neoplasm inaverage-risk population based on the established prediction rule and calculated theprevalence of advanced colorectal neoplasm of each risk level. The X2-test was used tomake comparisons of the prevalence of advanced colorectal neoplasm in different risklevels, age groups and genders.ResultsThere was a total of7541patients with complete colonoscopies. The prevalence ofcolorectal polyp, adenoma, advanced adenoma and cancer were29.1%,12.3%,4.2%and1.9%, respectively. The location of advanced colorectal adenomas（n=315） consisted ofdistal advanced adenoma (58.1%), proximal advanced adenoma (27.0%) and synchronous advanced adenoma (14.9%). The prevalence of advanced colorectal adenoma in male was5.4%, which was obviously higher than in female (2.9%)(P<0.001). Distributions ofadvanced colorectal adenoma in different genders had no statistical differences (P=0.860).The prevalence of advanced colorectal adenoma in≥50years group was5.1%, which wasobviously higher than <50years group (2.4%)(P<0.001). Distributions of advancedcolorectal adenoma in different age groups had no statistical differences(P=0.563).The developed prediction rule for advanced colorectal neoplasm in average-riskpopulation was composed of eight variables: age, sex, smoking, diabetes mellitus, greenvegetables, pickled food, fried food and white meat. The rule had a total score of0to14points. With the risk score increasing, the prevalence of advanced colorectal neoplasm roseobviously. In the population which risk evaluation scores was0-2points, the prevalence ofadvanced colorectal neoplasm were1.3-4.0%before70years and8.9-15.3%after70years;the prevalence of advanced colorectal neoplasm in these two groups had statisticaldifferences(P<0.01). In the population which risk evaluation scores was3-4points, theprevalence of advanced colorectal neoplasm were3.6%before45years and5.4-14.8%after45years; the prevalence of advanced colorectal neoplasm in these two groups hadstatistical differences(P<0.01). In the population which risk evaluation scores was＞4points, the prevalence of advanced colorectal neoplasm were9.8-22.7%and the prevalenceof advanced colorectal neoplasm in its40-44years group was9.8%which was higher than70-74years group in0-2points population. In total subjects, the prevalence of advancedcolorectal neoplasm were2.9-4.5%before55years and6.8-17.6%after55years; theprevalence of advanced colorectal neoplasms in these two groups had statisticaldifferences(P<0.01). The high-risk age of advanced colorectal neoplasms in male andfemale are older than45years and60years, respectively.ConclusionsThe prevalences of colorectal polyp and advanced adenoma in average-riskpopulation in male were higher than in female, and in≥50years group were higher than in<50years group. The distal advanced colorectal neoplasm account for the the largest shareof advanced colorectal neoplasms. The distributions of advanced colorectal neoplasm indifferent age groups and genders had no statistical differences.The optimal starting ages for colorectal cancer screening are different in different riskcrowd and genders. In different risk groups from low to high, screenings begin at70years,45years and40years, respectively. The optimal starting age for screening in women may be higher than that in men by15years.