168. FINAL REPORT: SIGNIFICANCE AND USEFULNESS OF PLASMA SUBSTANCE P LEVELS IN PREDICTING HIGH-RISK PATIENTS FOR ASPIRATION AFTER ESOPHAGEAL CANCER SURGERY

Abstract Background This is a report of the final analysis of a clinical study on prevention of aspiration after esophageal cancer surgery, following an interim analysis last year. Aspiration is regulated by laryngeal elevation and swallowing reflex. The swallowing reflex is controlled by substance P (SP), which is synthesized in the cervical sympathetic ganglia by stimulation of dopamine synthesized in the basal ganglia. It has been reported that one out of every four persons over the age of 60 in Japan has an asymptomatic cerebral infarction in the vicinity of the basal ganglia, and those may have a decreased swallowing reflex. Methods We investigated the correlation between preoperative plasma SP level and postoperative aspiration risk in patients with esophageal cancer (UMIN000032896). Subjects were patients with thoracic esophageal cancer scheduled for surgery. Preoperative plasma SP levels were measured at Japan Institute for the Control of the Aging (NIKKEN SEIL Co, Ltd) using Enzo SP ELISA kit (Enzo Biochem Inc.), and the correlation with the presence of unexpurgated laryngeal penetration or aspiration (defined as aspiration risk) by postoperative videofluorography (VF) was examined. Results Preoperative plasma SP levels and postoperative VF were evaluated in 111 patients. ◆Mean preoperative plasma SP levels in patients at risk of aspiration were lower than in those without aspiration risk (2.1 vs. 2.6 ng/ml, p = 0.095). ◆Patients were divided into 4 groups based on preoperative plasma SP value = 2.8 ng/ml (the value with the greatest sensitivity for predicting aspiration risk) and the presence of pharyngeal residue (PR) in preoperative VF, and compared with the risk of aspiration in postoperative VF, revealing a significantly higher postoperative aspiration risk in group A (Low SP and PR+) (Table) (p = 0.01). Conclusion Patients with low preoperative plasma SP were associated with a high postoperative aspiration risk, especially in patients with preoperative plasma SP < 2.8 ng/ml and pharyngeal residue in preoperative VF, suggesting that preoperative measurement of plasma SP and evaluation of pharyngeal residue by VF may be useful as indicators for predicting postoperative aspiration risk due to decreased swallowing reflex.