Piecemeal Resection and Advanced Histology Independently Predict Local Recurrence After Colorectal Snare-based Endoscopic Resection: a Time-to-event Cohort Study
Conditions: Colo-rectal Cancer
Sponsor: University of Sao Paulo

 
 
Piecemeal resection and advanced histology independently predict local 
recurrence after colorectal snare-based endoscopic resection: a 
time-to-event cohort study 
 
 
 
 
 
 
 
 
 
 
Study Protocol and Statistical Analysis Plan 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
February 24, 2026 

Brief summary 
This retrospective time-to-event cohort study aims to identify clinical, endoscopic, and 
histopathological variables associated with local recurrence after colorectal snare 
polypectomy. The study includes 255 consecutive adult patients who underwent 
snare-based colorectal polypectomy at a tertiary referral center between 2023 and 2025 and 
completed at least one surveillance colonoscopy. The primary outcome is local recurrence at 
the previous resection site. Secondary outcomes include metachronous adenoma and 
procedure-related adverse events. Time-to-event analyses will be performed to identify 
independent predictors of recurrence. 
Detailed description 
Endoscopic resection is one of the main strategies for colorectal cancer prevention. Snare 
polypectomy, with or without electrocautery, is widely performed; however, predictors of 
post-resection local recurrence remain incompletely understood. 
This study is a retrospective observational cohort conducted at Hospital das Clínicas, 
Ribeirão Preto Medical School, University of São Paulo. We included consecutive adult 
patients who underwent colorectal snare polypectomy between 2023 and 2025 and 
completed at least one surveillance colonoscopy. 
Lesions were characterized according to size, location, Paris classification, resection 
technique (en bloc or piecemeal), and histopathological findings. Advanced histology was 
defined as high-grade dysplasia and/or intramucosal adenocarcinoma (Tis). Lesion size was 
dichotomized as <10 mm or ≥10 mm, based on the maximum lesion diameter per patient. 
The primary outcome is local recurrence, defined as detection of adenomatous tissue at the 
previous resection scar or at the same topographic site. Time-to-event analyses using 
Kaplan-Meier and Cox proportional hazards models will be performed to identify 
independent predictors. Secondary outcomes include metachronous adenomas and 
procedure-related adverse events. 
Study type 
Observational 
Observational study model 
Cohort 
Time perspective 
Retrospective 
Enrollment 
255 participants 

Study start date 
January 2023 
Primary completion date 
December 2025 
Study completion date 
December 2025 (data analysis and follow-up completion) 
Outcome measures 
Primary outcome measure 
Local recurrence 
-​
Definition: adenomatous lesion detected at the prior resection scar or same 
topographic site; 
-​
Time frame: from index polypectomy to first surveillance colonoscopy (time-to-event 
analysis);​
 
Secondary outcome measures 
Metachronous adenoma 
-​
Definition: new adenomatous lesion detected at a site different from the original 
resection area; 
-​
Time frame: at surveillance colonoscopy;​
 
Procedure-related adverse events 
-​
Includes: perforation, post-polypectomy syndrome, clinically significant delayed 
bleeding, 30-day readmission, need for surgery, and mortality; 
-​
Time frame: within 30 days of index procedure;​
 
Eligibility criteria 
Inclusion criteria 
-​
Age ≥18 years; 
-​
Underwent colorectal snare polypectomy (with or without electrocautery); 
-​
Histopathological diagnosis available; 
-​
At least one surveillance colonoscopy completed;​
 

Exclusion criteria 
-​
No post-polypectomy surveillance colonoscopy; 
-​
Missing essential clinical or pathological data;​
 
Sex 
All 
Gender based 
No 
Age limits 
18 Years and older 
Accepts healthy volunteers 
No 
Sampling method 
Non-Probability Sample (Consecutive Sampling) 
Study population 
Adult patients undergoing colorectal snare polypectomy at a tertiary referral center between 
2023 and 2025 who completed surveillance colonoscopy. 
Study setting 
Hospital das Clínicas, Ribeirão Preto Medical School, University of São Paulo – Ribeirão 
Preto, São Paulo, Brazil. 
Statistical analysis plan 
Descriptive statistics will summarize baseline characteristics. Time-to-event analyses will be 
conducted using Kaplan-Meier survival curves, with comparisons by log-rank test. 
Multivariable Cox proportional hazards regression models will identify independent 
predictors of local recurrence. Hazard ratios (HR) with 95% confidence intervals will be 
reported. 
Analyses will focus primarily on local recurrence. Metachronous adenoma and adverse 
events will be analyzed descriptively and, when appropriate, using regression modeling. 
Ethical oversight 

The study protocol was reviewed and approved by the Research Ethics Committee of the 
Hospital das Clínicas da Faculdade de Medicina de Ribeirão Preto, University of São Paulo 
(HCFMRP–USP) (CAAE 94262925.8.0000.5440; Opinion No. 8.027.384). 
Given the retrospective design, based exclusively on medical record review, with no direct 
patient contact and no study-related interventions, and considering the implementation of 
strict confidentiality safeguards, the Research Ethics Committee granted a waiver of 
informed consent. 
All data were anonymized prior to analysis and handled in accordance with institutional 
regulations and the Brazilian General Data Protection Law (LGPD – Law No. 13.709/2018).