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Objectives: To clarify whether self-expandable metallic stent (SEMS) placement for obstructive colorectal cancer (CRC) increases perineural invasion (PNI), thereby worsening the prognosis. Methods: In total, 1022 patients with pathological T3 or T4 colon or rectosigmoid cancer who underwent resection were retrospectively reviewed. The study patients were divided into a no obstruction group (n=693), obstruction without stent group (n=251), and obstruction with stent group (n=78), and factors demonstrating an independent association with PNI, the difference in PNI incidence and severity between groups, and the association between PNI and the duration from SEMS placement to surgery were investigated. Survival analysis was performed for each group. Results: On multivariate analysis, SEMS placement (hazard ratio [HR]: 2.08) was independently associated with PNI whereas SEMS placement was not. PNI occurred in 39%, 45%, and 68% of the no obstruction, obstruction without stent, and obstruction with stent group, respectively. In the obstruction with stent group, the proportion of PNI was not associated with the duration from SEMS placement to surgery. Extramural PNI, an advanced form of PNI, demonstrated no increase with increasing interval. The five-year OS was 86.3%, 76.7%, and 73.1% in no obstruction, obstruction without stent, and obstruction with stent group, respectively. On multivariate analysis, obstruction was an independent risk factor of decreased OS (HR: 1.57) whereas SEMS placement was not. Conclusions: The prognosis was comparable between patients with SEMS placement and those with an obstruction who did not undergo SEMS placement, thus demonstrating that SEMS is a viable, therapeutic option for BTS.