Peritoneal metastasis as a predictive factor for nab-paclitaxel in patients with pretreated advanced gastric cancer: an exploratory analysis of the phase III ABSOLUTE trial

Background In the ABSOLUTE trial, weekly nanoparticle albumin-bound paclitaxel (w-nab-PTX) showed non-inferiority to weekly solvent-based paclitaxel (w-sb-PTX) for overall survival (OS). Thus, w-nab-PTX might be an option for second-line chemotherapy in advanced gastric cancer (AGC). However, predictive factors for efficacies of these agents have not been evaluated. Methods Patients previously enrolled in the ABSOLUTE trial were divided into apparent peritoneal metastasis group (PM group) and no apparent peritoneal metastasis group (no PM group) based on baseline imaging evaluated by RECIST ver. 1.1 criteria and amount of ascites. OS, progression-free survival, and overall response rate were compared between two arms in each group. Results This study included 240 and 243 patients in the w-nab-PTX and w-sb-PTX arms, respectively. In the PM group, the w-nab-PTX arm ( n = 88) had longer OS than the w-sb-PTX arm ( n = 103), and median survival time (MST) of 9.9 and 8.7 months [hazard ratio (HR) 0.63; 95% CI 0.45–0.88; P = 0.0060], respectively. In the no PM group, the w-nab-PTX arm ( n = 140) had shorter OS than the w-sb-PTX arm ( n = 152), and MST of 11.6 and 15.7 months (HR 1.40; 95% CI 1.06–1.86; P = 0.0180), respectively. After adjusting for prognostic factors, the HR for OS in the w-nab-PTX arm versus the w-sb-PTX arm was 0.59 (95% CI 0.42–0.83; P = 0.0023; PM group) and 1.34 (95% CI 1.01–1.78; P = 0.0414; no PM group), with significant interaction between treatment efficacy and presence of peritoneal metastasis ( P = 0.0003). Conclusions The presence of apparent peritoneal metastasis might be a predictive factor for selecting w-nab-PTX for pretreated AGC patients. Trial registration number JapicCTI-132059.