Combined Obesity and Muscle Impairment Phenotypes and Postoperative Outcomes in Patients Undergoing Colorectal Cancer Surgery: A Prospective Observational Study.

BACKGROUND: The coexistence of obesity and muscle impairment may adversely affect postoperative outcomes in patients undergoing colorectal cancer (CRC) surgery. This study aimed to investigate the association between combined obesity and muscle impairment phenotypes and short-term postoperative outcomes in patients undergoing colorectal cancer surgery. METHODS: In this prospective observational study, 300 patients undergoing elective colorectal cancer surgery were classified into four mutually exclusive phenotypes according to obesity and muscle status: non-obese without muscle impairment, obesity only, muscle impairment only, and obesity with muscle impairment. Obesity was defined as a body mass index ≥30 kg/m2, while muscle impairment was determined according to predefined muscle-related criteria. Demographic, clinical, nutritional, and physical activity data were collected preoperatively. Postoperative outcomes were assessed during a 30-day follow-up period. Continuous outcomes were analyzed using multivariable analysis of covariance with estimated marginal means, while binary outcomes were analyzed using multivariable logistic regression when the number of events was sufficient for reliable model estimation. RESULTS: Of the 300 patients, 29 (9.7%) had neither obesity nor muscle impairment, 51 (17.0%) had obesity only, 58 (19.3%) had muscle impairment only, and 162 (54.0%) had both obesity and muscle impairment. After adjustment for clinically relevant confounders, patients with obesity and muscle impairment had longer hospital stays than those without either condition (adjusted mean difference, 2.82 days; 95% CI, 2.48-3.17; P < 0.001) and those with obesity only (1.21 days; 95% CI, 0.93-1.49; P < 0.001). Surgery duration was also longer in the obesity-only and obesity-with-muscle-impairment groups compared with patients without either condition (11.91 min; 95% CI, 6.59-17.23; P < 0.001 and 11.89 min; 95% CI, 7.30-16.48; P < 0.001, respectively). Postoperative pain was higher in the obesity-only, muscle-impairment-only, and obesity-with-muscle-impairment groups compared with the reference group, with adjusted mean differences of 1.82, 2.33, and 2.08 points, respectively (all P < 0.001). Differences in binary postoperative complications were not statistically significant. CONCLUSION: The coexistence of obesity and muscle impairment was common among patients undergoing colorectal cancer surgery and was associated with longer hospitalization, longer operative duration, and greater postoperative pain. These findings support preoperative assessment of both obesity and muscle status to improve perioperative risk stratification in patients undergoing colorectal cancer surgery.