Colorectal cancer (CRC) is a prevalent disease with a high mortality rate and its incidence is increasing worldwide.1 It is the third most common type of cancer and the second cause of cancer-related death across the globe.2 In 2020 in Argentina, approximately 130,000 new cases of cancer were diagnosed.3 CRC was in second place, accounting for 12.1% of all the diagnoses2,3 and 12.4% of cancer-related deaths in the same period.4

Pathophysiologically, CRC derives from colorectal polyps originating from normal mucosa that, through genetic and epigenetic changes, progress into malignant tumors, during a process that takes an estimated 10 years.5,6 In this context, early detection of CRC precursory lesions or lesions in their initial stages could prevent the subsequent development of the disease.6,7 Therefore, colonoscopy has become one of the methods of choice for CRC screening thanks to its diagnostic and therapeutic capacities. In addition, clinical practice guidelines recommend periodic surveillance colonoscopy after the removal of a colonic adenoma, for the purpose of reducing the incidence and mortality of CRC. The risk of developing advanced adenoma and metachronous CRC is related to findings in the baseline colonoscopy.8

Different studies, the majority of which are observational, suggest a reduced incidence and mortality in CRC by using colonoscopy as the screening method.6,9 A study conducted in a Caribbean country reported CRC detection at earlier stages through screening colonoscopy, compared with its symptomatic detection.10 The first randomized clinical trial was recently published, in which there was a reduced risk of CRC in patients who were invited to undergo screening, compared with those who were not.11

From another perspective, national and international studies have shown that CRC screening is a cost-effective intervention, compared with no intervention, in terms of quality-adjusted life years.12 Since 2010, Argentina has had a CRC early detection and prevention program for persons between 50 and 75 years of age.13 However, there is no local information available on the characteristics of patients at standard risk that undergo colonoscopy for CRC screening, nor endoscopic findings of those studies.

Therefore, we decided to conduct an observational, cross-sectional study to estimate the prevalence of malignant lesions consistent with CRC in a first screening endoscopy, as well as to describe the endoscopic and anatomopathologic findings and the characteristics of the patients that underwent a screening colonoscopy for CRC.

A cross-sectional study was designed. The sample consisted of patients between 50 and 79 years of age, all with a prepaid healthcare plan at the same tertiary care hospital, who underwent their first colonoscopy as screening for CRC, within the time frame of January 2013 and December 2022. The reason for the colonoscopy was identified in the patient report made by the gastroenterologist who performed the examination. Demographic data, colonoscopy findings that included biopsy results, and the later diagnoses of the patients were collected to detect the development of CRC. Patients with a history of previous lower endoscopic studies or with a diagnosis of CRC prior to the first colonoscopy were excluded. The analysis included all the patients that met the inclusion criteria, with no exclusion criterion. CRC diagnosis was considered a consequence of colonoscopy in the patients whose biopsy from the procedure showed a lesion consistent with malignancy, defined in the anatomopathologic report with the terms, “carcinoma” and “colorectal origin”. The remaining later diagnoses were considered unrelated to the first endoscopy. The study was carried out at an advanced specialty hospital located in Buenos Aires, Argentina, that also acts as its own private healthcare provider, with approximately 181,000 affiliates in December 2022. Seven operating rooms are available to the Gastroenterology Department and about 100 endoscopic examinations are performed daily.

During the study period, 28,286 patients underwent colonoscopy as their first endoscopic examination. Of those patients, 19,222 (68%) were referred for colonoscopy as part of the screening process for individuals at an average risk for developing CRC. Table 1 shows the other indications for colonoscopy, outside of screening, of which gastrointestinal bleeding and change in bowel habits were the principal causes.

The mean age of the screened patients was 61 years (55-68 IQR), and 59.5% were women. A total of 999 patients (5.2%) were between 76 and 79 years of age when undergoing the colonoscopy. The mean annual prevalence of screening colonoscopy performed in men in the age group analyzed was 3.06 patients/year (95% CI 2.54-3.59), whereas it was 2.79 patients/year (95% CI 2.24-3.34) in women. There were no significant differences between sexes (p = 0.428). Fig. 1 shows the distribution of screening adherence over the years, with no substantial changes, except for 2020. The most commonly reported comorbidities are shown in Table 2, with high blood pressure at 41.2%, overweight at 39.9%, obesity at 25.3%, and smokers or ex-smokers at 24.9%. In the 6 months prior to the colonoscopy, only 3.5% (n = 668) of the patients had undergone a fecal occult blood test (FOBT) as a screening exam, of which 49.6% were positive.

Figure 1.

Prevalence of adherence to colonoscopy as a screening method over the years, differentiated by sex.

Table 3 describes the study’s findings. Polyps (36.7%) and diverticula (35.5%) were the most common lesions. Of the polyps identified, 88.2% (n = 6,239) were extirpated during the same procedure. There was a 1.04% prevalence of lesions with macroscopic characteristics suggestive of malignancy (e.g., vegetative, ulcerated, or friable lesions) in the colonoscopy (95% CI 0.9-1.19), and this type of lesion was detected in 201 patients. Biopsies were performed on 5,936 patients (30.8%) during the endoscopic procedure.

The prevalence of lesions consistent with CRC in the first colonoscopy was 0.6% (n = 118, 95% CI 0.50-0.72), with a predominance of low-grade adenocarcinoma (72.9%), whereas 21.2% were described as adenocarcinoma in situ or intramucosal adenocarcinoma. The adenoma detection rate (ADR) was 25.3%. The most frequent histologic finding was tubular adenoma, found in 18.8% (n = 3,617) of the endoscopic studies. In addition, 699 patients (3.6%) presented with adenomas with a villous component (villous characteristics in more than 25% of the adenoma) and 2.2% (n = 429) with serrated adenomas. Table 4 shows the rest of the histologic findings.

A total of 220 patients (1.14%) required hospitalization in a 30-day post-procedure window of the immediate follow-up period, and 5 of them were hospitalized more than once during that time interval. Median hospital stay was 2.37 days, with an interhospital mortality rate of 0%. The most common causes of hospitalization were gastrointestinal-related (37.6%), followed by trauma (8.8%) and cardiologic (7.5%) events. Twenty-five of those hospitalizations (11.1%) were considered associated with the endoscopic procedure, identifying 16 cases of gastrointestinal bleeding, 6 endoscopy-associated infections, and 3 perforations.

In our study population, the prevalence of CRC in the colonoscopies performed was 0.6% (95% CI 0.5-0.72%). The majority of the tumors were low-grade adenocarcinoma (72.9%) and the remaining 21.2% were carcinoma in situ or intramucosal carcinoma. Said prevalence percentage is somewhat lower than the results from a German cohort that included almost 3,000,000 screening colonoscopies, in which carcinoma was detected in 0.9% of cases, and most of them (47%) were in the initial stages.14 However, our figures are comparable with those of a recent meta-analysis of Latin American studies, which reported an overall CRC detection rate of 0.4% (95% CI 0.1%-0.8%) in patients that were screened.15 These comparisons point out the geographic and methodological variations in the prevalence of CRC, underlining the importance of specific contexts in interpreting results and planning screening strategies.

Participant age (61 years) was consistent with the recommendations of the majority of guidelines and coincided with that reported in an Austrian cohort.16 Despite the Argentinian national CRC screening recommendation, patients above 75 years of age have undergone screening colonoscopy. In our study, 5% of the participants included were above 75 years of age. Even though findings in that subgroup are beyond the scope of the present work, a deeper examination of screening benefits in that age group is important to carry out.

CRC screening is the only cancer screening program offered to both men and women,17 and so adherence to the different CRC detection programs by sex has been evaluated, albeit with disparate results. For example, a study conducted in Hong Kong showed a greater number of females participating in a CRC screening program,18 whereas an Italian study reported similar participation by men and women, as did a retrospective cohort study conducted in the United States.18–20 In our analysis, screening adherence was similar in the two sexes, but future studies are needed to determine if there is an actual clinical difference between males and females, regarding screening adherence. The prevalence of colonoscopy adherence remained stable over the past 10 years, with the exception of a dramatic decline in 2020, most likely due to the obligatory isolation in place during the COVID-19 pandemic that largely reduced the performance of preventive strategies. The most frequent findings reported were the presence of polyps (36.7%), similar to that described in an Argentinian national retrospective study,21 followed by diverticula (35.5%). The polyp detection rate is considered an indicator of adequate inspection in screening or diagnostic colonoscopy and correlates well with the ADR.22,23 Local recommendations suggest a polyp detection rate of 40% or higher.24 As we stated before, the ADR is another quality indicator, with values of 25% or higher (20-25% in women and 25-30% in men)25 considered appropriate. It is a surrogate marker for a meticulous inspection of the colonic mucosa and is inversely related to the risk of CRC and death by cancer. Our study found an ADR of 25.3%, meeting the reference standards.

Regarding the complications related to the procedure, 220 participants (1.14%) had to be hospitalized for any cause within 30 days from the colonoscopy, which was very similar to the 1.11% reported in a cohort in the United States. Hospitalization was more frequent in patients that required polypectomy. Of the total number of hospitalizations, 11.1% were directly related to the endoscopic procedure. A low quantity of perforations (0.015%), bleeding (0.08%), and infections (0.03%) was identified and was less frequent than in the aforementioned US cohort. This could be associated with the large volume of procedures carried out at our center and the expertise of the endoscopists performing them.26

One of the strengths of the present study is the large sample size, providing robust results and increasing study population representativeness. Nevertheless, the fact that the study participants belonged to a prepaid medical healthcare system could affect the generalization of the results.

Another study limitation was the use of secondary databases. Participant inclusion was based on codifications taken from electronic clinical histories, which could result in the inclusion of patients that were not at standard risk for developing CRC. At any rate, data extraction through an electronic register improves the accuracy and reliability of the collected information.

Concerning hospitalizations, a manual review of the patient histories was conducted by experts to determine whether they were related to the endoscopic procedure. Nevertheless, only events such as perforations, gastrointestinal bleeds, or intra-abdominal infections were considered complications of the procedure. In contrast, hospitalizations due to cardiac causes that may or may not have been related to the preparation for the procedure were not, which could have been underestimated.

The main strength of our study was its contribution to local information on the characteristics of the population undergoing CRC screening outside of an institutional program and its endoscopic findings, thanks to the large number of patients treated at our center.

In conclusion, the present study provides relevant information on the characteristics of the patient population that undergoes CRC screening at our center, as well as on the endoscopic findings and the detection rates of premalignant and malignant lesions. These data contribute to a better understanding of the profile of patients that access CRC screening and the characteristics of the detected lesions, providing a solid descriptive base upon which clinical practices, diagnostic method quality, and results can be evaluated, in the context of screening programs in average-risk populations.

No financial support was received in relation to this study/article.