Neoadjuvant docetaxel, oxaliplatin, and S-1 therapy for patients with large type 3 or type 4 gastric cancer: short-term outcomes of a multicenter, phase II study (OGSG1902).

[BACKGROUND] Large type 3 (≥ 8 cm) and type 4 gastric cancers (GCs) have poor prognoses and necessitate multidisciplinary treatment. A multi-institutional phase II study (OGSG1902) was conducted to assess the efficacy and safety of neoadjuvant chemotherapy (NAC) with docetaxel, oxaliplatin, and S-1 (DOS) in these patients.

[METHODS] Patients with large type 3 or type 4 GC without distant metastasis, except for positive peritoneal cytology (CY), were enrolled. Patients received three courses of neoadjuvant DOS therapy (docetaxel 40 mg/m and oxaliplatin 100 mg/m on day 1 via intravenous infusion, and S-1 80 mg/m orally for 14 days, repeated every 3 weeks) followed by gastrectomy. After R0 resection, adjuvant docetaxel/S-1 therapy was administered for 1 year.

[RESULTS] From October 2019 to February 2022, 48 patients were enrolled. NAC was completed in 91.7% of patients. The R0 resection rate was 89.6%. The pathological response rate (Grade 1b-3) was 66.7%. Among patients with measurable lesions, the response rate was 50.0%. The CY-negative conversion rate was 80.0%, and the protocol completion rate was 45.8%. Grade 3 or 4 adverse events during NAC, including neutropenia and appetite loss, occurred in 37.5% of patients. Major postoperative complications (Clavien-Dindo Grade IIIa or higher) were observed in 2.1% of patients.

[CONCLUSIONS] NAC with DOS for large type 3 or type 4 GC followed by gastrectomy demonstrated promising efficacy, high pathological response rates, and an acceptable toxicity profile. Further evaluation of long-term survival outcomes is ongoing.