Comparison of PSOX (paclitaxel, oxaliplatin, S-1) and SOX (oxaliplatin, S-1) as postoperative adjuvant chemotherapy for stage II-III gastric cancer.

Background: Adjuvant chemotherapy is the conventional treatment for stage II and III gastric cancer(GC). Postoperative doublet chemotherapy has consistently shown improved survival outcomes in advanced-stage GC patients compared to single-agent regimens. Triplet regimens have shown significant survival benefits in the perioperative settings. This retrospective study evaluated the efficacy and safety of paclitaxel/S-1/oxaliplatin (PSOX) compared to S-1/oxaliplatin (SOX) as postoperative adjuvant chemotherapy in stage II-III GC patients following D2 gastrectomy.

Methods: A retrospective review was conducted on patients with histologically confirmed stage II-III gastric cancer who underwent D2 gastrectomy at Jiangsu Cancer Hospital, categorizing them into two groups. A total of 75 patients were included in PSOX group and 81 patients in the SOX group between April 2018 and August 2021. Patients in PSOX group received paclitaxel (120 mg/m), oxaliplatin (100 mg/m) and S-1 (80 - 60 mg/d) per cycle, while those patients in SOX group were administrated oxaliplatin (130 mg/m) and S-1 (80-120 mg/d) per cycle. Patients from both groups were matched in a 1:1 ratio using propensity scores to assess differences in disease-free survival (DFS) and safety.

Results: The 3-year DFS rate was 78.2% for the PSOX group and 74.0% for the SOX group (P = 0.355), with a hazard ratio for peritoneal relapse of 0.287 (95% CI, 0.090-0.915; P = 0.035). Subgroup analysis indicated that stage IIIC GC patients in the PSOX group had a higher DFS rate than those in the SOX group(P = 0.032). Grade 3 or 4 adverse events, as per the National Cancer Institute Common Toxicity Criteria, such as leucopenia (10.6% vs. 4.5%), neutropenia (10.6% vs. 9.1%), nausea/vomiting (4.5% vs. 3.0%), and diarrhea (4.5% vs. 3.0%) were relatively common in the PSOX group compared to the SOX group, with no statistically significant differences between the two groups.

Conclusion: Our findings suggested that adjuvant PSOX chemotherapy offers superior survival benefits compared to the SOX regimen in patients with staged IIIC GC after D2 gastrectomy. The incidence of adverse events with PSOX chemotherapy was comparable to that of SOX chemotherapy.