Does Tumor Sidedness Matter After Curative Surgery in Colorectal Cancer? A Retrospective Cohort Study on Recurrence...

The prognostic and predictive relevance of primary tumor sideness in colorectal cancer (CRC) has garnered growing interest. While clinical and molecular differences between right-sided (RS), left-sided (LS) and rectal (RT) tumors are well established in metastatic disease, their impact in non-metastatic, surgically treated patients remains less clear. This study aims to evaluate whether tumor location influences recurrence patterns and post-recurrence survival (PRS) following curative-intent resection for CRC. Patients and Methods We conducted a retrospective cohort study including 1,425 patients with histologically confirmed stage I-III colorectal adenocarcinoma who underwent R0 resection.

Tumor recurrence was observed in 22.4% of patients. However, recurrence site differed significantly by tumor location: RS tumors were more likely to develop peritoneal metastases (9.5% vs. 6.6% LS and 5.3% RT; p=0.044), whereas RT tumors had a higher incidence of pulmonary metastases (12.4% vs. 6.3% RS and 7.4% LS; p=0.004). PRS differed markedly: 36-month PRS was 21% for RS, 41% for LS, and 32% for RT (p=0.005). Multivariate analysis confirmed primary tumor location as an independent prognostic factor for PRS. RS tumors conferred a significantly higher risk of death post-recurrence compared to LS and RT tumors. Although tumor sidedness does not appear to influence overall recurrence rates after curative resection, it is associated with distinct metastatic patterns and significantly worse post-recurrence outcomes.

These findings highlight the need to incorporate tumor location into prognostic stratification and post-surgical surveillance strategies in CRC. Personalized follow-up protocols, based on tumor biology and recurrence risk, may improve long-term outcomes.