Efficacy and Safety of a 3-Weekly TS-1 Adjuvant Regimen in Advanced Gastric Cancer: A Pilot Study

TS-1 at 80 mg/m²/day for 4 weeks followed by a 2-week rest is standard adjuvant therapy for stage II/III Advanced Gastric Cancer (AGC). TS-1 for 1 year (8 courses) is highly recommended. We investigated the efficacy and safety of an adjuvant 3-weekly TS-1 regimen for AGC.

We analyzed 93 patients with stage II/III AGC who started 3-weekly adjuvant TS-1 therapy between Feb 2017 and May 2022 post-gastrectomy with D2 lymphadenectomy. The 3-weekly regimen was TS-1 at 80 mg/m²/day for 2 weeks, followed by a 1-week rest for 1 year (16 courses).

Among 93 patients, 12 (13%) had disease recurrence during follow-up (median 24.6 months, range 4.2%-63.3%). Seven (9.5%) with stage II (n = 73) and five (25%) with stage III (n = 20) experienced recurrence. Kaplan-Meier analysis estimated that Recurrence-Free Survival (RFS) rates at 1, 3, and 5 years were 92.0% (95% CI; 86.5%-97.9%), 84.7% (95% CI; 76.4%-93.9%), and 78.6% (95% CI; 65.8%-94.0%), respectively. Eighty patients (86%) completed the treatment; 25 (26.9%) needed dose reduction. Adverse events, mostly grade 1 or 2 diarrhea (28%) and nausea (20%), were manageable.

Our study revealed that the 3-weekly TS-1 regimen as adjuvant therapy exhibited good efficacy and manageable toxicity. This regimen as an adjuvant therapy for AGC should be evaluated in future studies.