Validation Trial of a Novel Marker of Delayed Chemotherapy-induced Emesis

Post hoc analyses of study data suggested that the ratio of substance P to 5-HIAA/creatinine was a novel marker associated with risk of developing delayed chemotherapy-induced emesis. In order to verify this finding, a new clinical trial was conducted to prospectively evaluate the marker in patients receiving chemotherapy of high emetic risk level. Treatment in this study was restricted to two doxorubicin and cyclophosphamide-containing regimens. Prior to chemotherapy, blood and urine samples were collected. Serum substance P and urine 5-HIAA and creatinine (Cr) were measured to calculate patient-specific ratios. The attending oncologist had the option to follow current antiemetic guidelines or the investigators’ recommendation based on the subject’s pretreatment marker ratio.Delayed chemotherapy-induced emesis was the primary symptom monitored.Calculated ratios were ranked highest to lowest using the previously identified value of >70 as the cutoff. Of the 36 patients enrolled in the study, 11 had ratios associated with increased risk of delayed emesis. Mean pretreatment ratios for patients with (+) and without (-) emesis were 74.2 and 48.8, respectively. Although non-parametric analysis indicated the between-emesis group variance was not significantly different, p=0.154, a clear trend was observed with a higher percentage of subjects exhibiting delayed symptoms with ratios >70.