A phase II study of S-1 therapy for patients with advanced and recurrent esophageal cancer resistant or intolerable to fluorouracil, platinum, and taxane therapy (OGSG 1404).

Background: Fluorouracil (FU), platinum (PT), and taxane (TAX) therapy was the standard chemotherapy for esophageal squamous cell carcinoma (ESCC) before the era of anti-programmed death-1 antibodies. The aim of this phase II trial was to evaluate the efficacy and safety of S-1 monotherapy for patients with recurrent or metastatic (R/M) ESCC resistant or intolerable to FU, PT, and TAX therapy.

Methods: Eligible patients had R/M ESCC; no prior S-1 use; were intolerant or refractory to prior FU, PT, and TAX therapy; aged ≧ 20 years; and Eastern Cooperative Oncology Group performance status 0 or 1. S-1 was administered orally from days 1 to 28, every 6 weeks until disease progression. The primary endpoint was the disease control rate (DCR) for each patient, assessed by Response Evaluation Criteria in Solid Tumors, version 1.1. Secondary endpoints were overall survival, progression-free survival, time to treatment failure, response rate, and toxicity.

Results: Between October 2015 and December 2017, 17 patients were recruited, and the trial was terminated because of slow accrual. The DCR was 46.7%. The response rate was 13.3%. The median progression-free survival was 2.0 months. The median time to treatment failure was 1.9 months. The median overall survival was 8.4 months, and the 1 year overall survival rate was 30.5%.

Conclusions: Although this trial closed early because of slow accrual, we observed modest clinical activity with S-1 in patients with R/M ESCC who could not tolerate or whose tumors were refractory to FU, PT, and TAX therapy.