Low blood orexin concentration as a predictor of increased nutritional risk and all-cause mortality after surgery for colorectal cancer.

Introduction: Orexin regulates food intake, as well as the development and progression of neoplasms.

Aim: The aim of this study was to determine associations between nutritional risk and status and neoplasm stage and prognosis in patients who underwent surgery for colorectal cancer (CRC).

Material and methods: In 84 consecutive patients undergoing surgery for CRC, serum orexin, nutritional risk and body composition (assessed by bioelectrical impedance analysis and cross-sectional area determined using abdominal CT) were evaluated before the operation and 3 months after the surgery. The long-term follow-up lasted 1296.0 ±617.7 days.

Results: Compared to CRC patients with a serum orexin concentration lower than the cutoff value (197.9 pg/ml) determined in ROC curve analysis in prediction of all-cause mortality during long-term follow-up, those with orexin concentrations equal to or higher than the cutoff value were, at baseline and at the 3-month visit, more likely to have a lower score on the nutritional NRS2002 and a higher score on functional scales, greater handgrip strength, and higher skeletal muscle mass, and were less likely to suffer perioperative complications and all-cause mortality (OR = 0.34; 95% CI: 0.13-0.89; p = 0.026) during the follow-up period. No statistically significant differences in tumor size, histopathological grade or clinical stage were found between CRC patient groups divided according to orexin blood concentration.

Conclusions: Serum orexin concentrations were found to be statistically significantly associated with patients' nutritional risk and status before surgery and at a 3-month follow-up visit, and with all-cause mortality during the 3.6-year follow-up.