Background: Combination of ramucirumab (RAM) + weekly paclitaxel (PTX) is recommended as a standard second-line therapy for unresectable or recurrent gastric cancer (GC). A recent phase II trial evaluating nab-PTX and RAM combination showed that nab-PTX+RAM is promising efficacy and tolerability as well as PTX+RAM. In subgroup analysis of another phase III trial (ABSOLUTE) comparing different nab-PTX scheduling with PTX, weekly nab-PTX was especially effective for the patients with peritoneal dissemination compared to PTX without RAM combination. Therefore, we hypothesized that nab-PTX+RAM would be more effective than PTX+RAM for patients with peritoneal dissemination. Methods: The P-SELECT trial (WJOG10617G) is an open-label randomized phase II study evaluating the safety and efficacy of PTX+RAM and nab-PTX+RAM in GC patients with peritoneal metastasis. Key eligibility criteria were: 1) histologically proven adenocarcinoma, 2) unresectable or recurrent gastric cancer, 3) peritoneal dissemination, 4) intolerance or refractory to first-line therapy including fluoropyrimidines, 5) PS 0–2. Peritoneal dissemination was confirmed by either contrast enema/enterography, CT scan, clinical signs, or operative findings (including exploratory laparoscopy). The primary endpoint was overall survival (OS), and the secondary endpoints were progression-free survival (PFS), objective response rate (ORR), disease control rate (DCR), ascites control rate, safety, and neuropathy-specific quality of life. 105 subjects were required to maintain the power of ≥70% expecting the hazard ratio (HR) of 0.90 in OS. The study was conducted in 58 centers of the West Japan Oncology Group. Results: A total of 105 patients (median age 67; M:F 66:39) were randomized (53 patients in PTX+RAM and 52 in nab-PTX+RAM). Moderate and massive amount of ascites was observed in 39.0% of patients. Median OS was 8.1 months in PTX+RAM and 7.2 months in nab-PTX+RAM (HR 1.04, 95% confidence interval [CI] 0.67–1.61, P = 0.63). Median PFS was 5.1 months in PTX+RAM and 3.9 months in nab-PTX+RAM (HR 1.04, 95% CI 0.69–1.56, P = 0.89). The ORR and DCR for PTX+RAM and nab-PTX+RAM were 20.7% vs. 20.0% (P = 0.99) and 77.4% vs. 63.5% (P = 0.15), respectively. The ascites control rate was 86.1% in PTX+RAM and 70.3% in nab-PTX+RAM (P = 0.07). The incidence of grade 3/4 neuropathy was higher in nab-PTX+RAM (7.5% vs 17.6%, P = 0.14), whereas there was no difference in neuropathy-specific quality of life between the two groups. The incidence of febrile neutropenia was higher in PTX+RAM (11.3% vs 5.9%, P = 0.49). Conclusions: The potential difference in efficacies between nab-PTX+RAM and PTX+RAM was not shown in advanced gastric cancer with peritoneal dissemination. The results of the pre-planned translational research will be available soon. Clinical trial information: jRCTs031180022.