The efficacy and toxicity of adjuvant S-1 schedule with 2-week administration followed by 1-week rest in gastric cancer patients

Abstract

Background: This study aimed to investigate the clinical outcome of adjuvant S-1 with 2-week administration followed by a 1-week rest for locally advanced gastric cancer (GC) patients. Methods:The current study was a single retrospective cohort study that focused on the efficacy and toxicity of adjuvant S-1 with a 3-week schedule. A total of 60 patients who underwent total or subtotal gastrectomy plus D2 lymph node dissection and adjuvant S-1 treatment were identified. S-1 treatment began within 4 weeks after the operation; it was administered orally for 2 weeks, followed by a 1-week rest. The dose of S-1 was adjusted depending on adverse events (AEs), with at least 80 mg administered daily. The completion of 1-year S-1 was defined as S-1 continuation for 1 year with over 70% of the planned dose.Patients were followed up with for 5 years postoperatively and underwent hematologic tests and assessments of clinical symptoms every 3-6 weeks for 1 year after surgery. Computed tomography of the abdomen and panendoscopy were performed every 6 months during the first 2 years and at 1-year intervals thereafter until year 5 after surgery. Results:The completion rate of 1-year adjuvant S-1 was 71.7%, and the 3-year disease-free survival and overall survival rates were 70.2% and 79.5%, respectively. Seventeen patients did not complete S-1 for 1 year, including 11 patients with tumor recurrence and 6 patients who developed intolerance. Most AEs of S-1 were grade 1-2, and the most frequent AEs (>20%) included anemia, fatigue, pigmentation, nausea, and diarrhea. The most common grade 3-4 AE was fatigue, which was observed in 6.7% of patients. Most patients tolerated the side effects. Conclusions:The results of our study confirm that the efficacy and safety of schedule modification of adjuvant S-1 treatment in patients with GC who underwent gastrectomy with D2 lymph node dissection are equal to those in a previous phase 3 study.