Preoperative and Pathological Discrepancies in Colorectal Cancer: A Single-Institution Retrospective Analysis Based...

This study evaluated the concordance between preoperative clinical and postoperative pathological staging in stage II-III colorectal cancer (CRC), stratified by BRAF V600E mutation and mismatch repair (MMR) status.

We retrospectively analyzed 754 patients who underwent curative resection for stage II-III CRC between 2015 and 2023. Molecular subtypes were defined as proficient MMR with BRAF mutation (pMMR/BRAF-MT), proficient MMR without mutation (pMMR/BRAF-WT), or deficient MMR (dMMR). Concordance of T factor, N factor, and overall stage was classified as underdiagnosis, match, or overdiagnosis.

The cohort included 29 (3.8%) pMMR/BRAF-MT, 646 (85.7%) pMMR/BRAF-WT, and 79 (10.5%) dMMR cases. The overall concordance rates between clinical and pathological staging were 55.2% for the T factor, 39.9% for the N factor, and 50.4% for stage. N-factor concordance was lowest (39.9%), with pMMR/BRAF-MT showing the highest underdiagnosis (44.8%) and dMMR the highest overdiagnosis (50.6%). Multivariable analysis identified pMMR/BRAF-MT as an independent predictor of N-factor underestimation (OR 2.76, 95% CI 1.24-6.12, p=0.013). Survival analyses were exploratory and potentially underpowered because of the limited number of events.

Molecular subtype significantly affects staging accuracy in stage II-III CRC. BRAF-mutated and dMMR tumors are prone to under- and overstaging, respectively. These findings highlight the potential value of incorporating molecular subtype information into preoperative assessment to improve staging accuracy and guide optimal treatment planning.