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

## TL;DR

This pilot study evaluated a 3-weekly TS-1 regimen for advanced gastric cancer and found it to be effective with manageable side effects.

## Contribution

The study introduces a modified 3-weekly TS-1 regimen as a potential alternative for adjuvant therapy in advanced gastric cancer.

## Key findings

- Recurrence-free survival rates were 92.0%, 84.7%, and 78.6% at 1, 3, and 5 years, respectively.
- Most adverse events were mild (grade 1 or 2), with diarrhea and nausea being the most common.
- 86% of patients completed the treatment, and 26.9% required dose reductions.

## Abstract

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.