1. Description of the sample
Between May 2013 and June 2019, a total of 16,720 subjects underwent at least one colonoscopy during the first round of the Galician CRC screening program. We excluded 1013 subjects with CRC as the final diagnosis from this analysis. Therefore, we included in the analysis 15,707 patients with non-malignant lesions detected in the first round. After linking this data with the CMBD database, we identified 352 patients with any of the codes related to colorectal surgery. After verifying the clinical records, we confirmed that 162 underwent colorectal surgery related to participation in the screening program, four due to colonoscopy-related complications and 158 due to resection of colorectal lesions (Figure 1 and Table 1). The surgery rate was as follows: global: 10.3‰ (95% CI 8.7-11.9), due to colonoscopy complications: 0.2‰ (95% CI 0.005-0.5) due to resection of colorectal lesions: 10.0‰ (95% CI 8.5-11.6). In the seven hospitals taking part in the CRC screening program, the surgery rate ranged widely between 2.7‰ (95% CI 0.5-5.0) and 18.9‰ (95% CI 13.6-24.3). After excluding transanal surgeries (31) the colectomy rate was 8.3‰ (95% CI 6.9-9.8). The colectomy rate again ranged between 2.3‰ (95% CI 0.3-4.3) and 16.2‰ (95% CI 10.6-21.7). In Table 1, we outline the characteristics of the sample as well as the surgery rate according to dependent variables and in Supplementary Table 1 we show the same results referred to colectomies.
Seventy-one endoscopists from seven hospitals took part in the first round of the CRC screening program. The median number of colonoscopies performed was 278 (IQR 56-507) and median ADR was 65.3% (IQR 60.0%-70.08%). We classified endoscopists into quartiles according to number of colonoscopies performed and ADR. Finally, hospitals were classified into tertiary (three) and secondary (four).
2. Type of surgery and complications.
As shown in Table 2, the main surgical approach was laparoscopy (57.4%). The most common surgeries performed were right-sided interventions (51.3%) and transanal resections (19.1%). The median length of hospitalization was 6 days with minor and major complications in 28 (17.3%) and 12 (7.4%) patients, respectively. Only one patient died due to surgery. After discharge, complications were detected in 29 (18.1%) patients, mainly due to intestinal subocclusion (5), rectal bleeding (3), abdominal wall hernia (11), anastomotic stenosis (2) and change in bowel movements (3). After colectomy, intrahospital complications were detected in 34 (26%) patients, mostly minor (23) and complications after discharge in 28 patients (21.4%). In contrast, in hospital and out-of-hospital complications were detected in six (19.4%) and one (3.2%) patients after transanal surgery, respectively.
3. Characteristics of the resected colorectal lesions
As shown in Table 3, most surgically resected lesions were either right-sided (49.6%) or located in the rectum (22.2%). Median endoscopic size was 35 mm and most lesions were either sessile, flat or laterally spreading tumors. The lesions had a SMSA score above 12 in most cases (76.7%). An endoscopic resection was attempted in 23.5% of patients either in the work-up colonoscopy or in scheduled therapeutic colonoscopy. Median surgical size of the lesion was 25 mm and, as in the endoscopic histology, the most common histology was adenomatous (81.8%).
4. Factors associated with surgery.
During univariate analysis, several factors related to the patient (age), screening program (FIT result and number of baseline colonoscopies performed), characteristics of the lesions detected (number of polyps and adenomas, adenoma size and classification according to the European guidelines for CRC screening), endoscopist quality metrics (ADR and number of colonoscopies performed), and hospital complexity were significantly associated with the surgery rate as shown in Table 2. With respect to colectomy, we also identified several associated variables as shown in supplementary Table 1.
Finally, during multivariable logistic regression analysis, age ≥60 years (OR=1.57, 95% CI 1.11-2.23), female sex (OR=2.10, 95% CI 1.52-2.91), the European guidelines classification (high risk OR=67.94, 95% CI 24.87-185.59; intermediate risk OR=5.63, 95% CI 1.89-16.80: low risk OR=1.43; 95% CI 0.36-5.75), the endoscopist’s ADR (Q4 OR=0.44, 95% CI 0.28-0.68; Q3 OR=0.44, 95% CI 0.27-0.71; Q2 OR=0.71, 95% CI 0.44-1.14) and a third level hospital (OR=0.54; 95% CI 0.38-0.79) were independently associated with risk of surgery as shown in Table 4. After excluding transanal surgeries, the same variables were independently related to risk of colectomy: age ≥60 years (OR=1.93, 95% CI 1.30-2.89), female sex (OR=2.21, 95% CI 1.54-3.16), the European guidelines classification (high risk OR=53.21, 95% CI 19.36-146.18; intermediate risk OR=5.33, 95% CI 1.77-16.03; low risk OR=1.07; 95% CI 0.24-4.78), the endoscopist’s ADR (Q4 OR=0.37, 95% CI 0.23-0.61; Q3 OR=0.48, 95% CI 0.29-0.79; Q2 OR=0.58, 95% CI 0.34-1.00) and a third level hospital (OR=0.57; 95% CI 0.38-0.85).