Colorectal cancer (CRC) screening has increased the detection of benign polyps. Although most can be safely removed endoscopically, some patients are still referred for surgery due to technical or organizational limitations, resulting in avoidable overtreatment. This study aimed to determine the rate of avoidable surgery within the Catalan CRC Screening Program and to assess territorial variability in a FIT-based screening context.

A retrospective observational study was conducted including all participants aged 50–69 years with a positive fecal immunochemical test (FIT) who underwent colonoscopy between 2010 and 2020. Data from the Catalan CRC Screening Registry were cross-linked with the Catalonian Inpatient Minimum Basic Data Set (CMBD-AEA) using ICD-9 and ICD-10 codes to identify colorectal surgeries performed within 12 months after colonoscopy. Cases with CRC stage >pT1 or surgeries unrelated to screening were excluded. Surgery rates were calculated overall and by geographic area, classified as urban or rural.

 Among 93,035 colonoscopies (mean age 59.6 ± 5.7 years; 44.3% women), 1,427 surgeries were performed (1.53%; 95% CI 1.46–1.61), including 893 procedures for benign lesions (0.96%; 95% CI 0.90–1.02). Across territories, five areas showed rates close to the Catalan average, whereas four deviated markedly, with surgery for benign lesions ranging from <0.6% in highly specialized urban areas to 3–4% in rural regions. Colonoscopy-related complications occurred in 625 procedures (0.67%; 95% CI 0.62–0.73), of which 27 (0.03%) required surgery. CRC-pT1 was diagnosed in 1,378 examinations (1.48%; 95% CI 1.41–1.56), with 516 patients undergoing surgery (0.55%; 95% CI 0.51–0.60). 

A non-negligible proportion of surgeries following CRC screening are performed for benign lesions, reflecting territorial inequities and opportunities for improvement. Although the overall rate of overtreatment is low, optimization through advanced endoscopic training and structured referral pathways remains a key goal.