Perioperative and Oncological Outcomes of Colorectal Cancer Surgery in Obese Patients: A Multicenter Retrospective Study

ABSTRACT Background With global rising rates of obesity, surgeries for colorectal cancer (CRC) in obese patients are increasingly common. Although obesity may complicate surgical procedures and oncologically unbeneficial, its true clinical impact remains unclear. Methods Patients with stage I–IV CRC who underwent surgical resection between 2017 and 2019 were enrolled from a prefecture‐wide multicenter database. Patients were categorized based on body mass index (BMI) into non‐obesity (BMI < 25 kg/m 2 ), mild‐obesity (BMI ≥ 25 and < 30 kg/m 2 ), and severe‐obesity (BMI ≥ 30 kg/m 2 ) groups. Perioperative outcomes, long‐term survival, and lymph node metrics, including the log odds of positive lymph nodes (LODDS). Results Among 2905 patients, 2283 were non‐obesity, 576 mild‐obesity, and 91 severe‐obesity. Younger, more often male, and had higher American Society of Anesthesiologists (ASA) class and Charlson Comorbidity Index scores are included in obesity group. Operative time and blood loss increased with BMI, while the number of retrieved lymph nodes and D3 dissection rates declined. Postoperative complications and hospital stay showed no significant differences. While recurrence‐free survival (RFS) and overall survival (OS) were comparable across BMI groups, obese patients had a higher proportion of LODDS ≥ −0.7. In stage III patients, LODDS ≥ −0.7 was more strongly associated with recurrence and poor prognosis in the obese subgroup. Conclusions Obesity is associated with increased surgical complexity and limited pathological lymph node evaluation. Among stage III CRC patients, impaired nodal stratification—as reflected by elevated LODDS—may contribute to poorer prognosis in the obese population, highlighting the need for tailored oncological strategies.