Measuring serum and drainage fluid interleukin-6 and tumor necrosis factor-α levels for early detection of infectious complications after minimally invasive surgery for gastric cancer

Objective: Interleukin-6 (IL-6) and tumor necrosis factor-alpha (TNF-alpha) are inflammatory cytokines produced in response to biological invasion or infection. Their levels are elevated in the blood and locally. We examined whether measuring IL-6 and TNF-alpha levels in serum or drainage fluid on postoperative day (POD) 1 could detect infectious complications after minimally invasive surgery for gastric cancer. Methods: This cohort study included 205 consecutive patients who underwent laparoscopic or robot-assisted gastrectomy for gastric cancer between November 2020 and July 2023. We measured serum and drainage fluid IL-6 and TNF-alpha levels on POD 1 after gastrectomy. Receiver operating characteristic (ROC) curves were created to compare the diagnostic values of each cytokine and serum C-reactive protein levels for detecting postoperative infectious complications. Results: IL-6 and TNF-alpha levels in the serum or drainage fluid were significantly higher in patients with an infectious complication. In addition, drainage fluid IL-6 levels were significantly different in patients with versus without intra-abdominal abscess. In the ROC curve analysis, serum and drainage fluid IL-6 had the highest AUC values for any infectious complication and intra-abdominal abscess, respectively. POD 1 serum IL-6 level above 47 pg/mL could detect any infectious complication with sensitivity of 74.1 % and specificity of 71.8 %. POD 1 drainage fluid IL-6 level above 14,750 pg/mL had 100 % sensitivity for detecting intra-abdominal abscess with specificity of 56.0 %. Conclusions: Measurement of IL-6 levels in blood and drainage fluid on POD 1 is valuable for early detection of postoperative infectious complications or intra-abdominal abscess after gastric cancer surgery.