Feasibility study of adjuvant chemotherapy with S-1 after curative esophagectomy following neoadjuvant chemotherapy for esophageal cancer

Background Despite advances in surgical techniques, long-term survival after esophagectomy for esophageal cancer remains unacceptably low, and more effective perioperative chemotherapy is expected. However, an important concern regarding the application of postoperative adjuvant chemotherapy is treatment toxicity. We aimed to evaluate the feasibility of adjuvant chemotherapy with S-1 in patients after esophagectomy. Methods We investigated the tolerability of a 2-week administration followed by 1-week rest regimen of S1 as postoperative adjuvant therapy in 20 patients with esophageal squamous cell carcinoma who received neoadjuvant chemotherapy (NAC) and 22 patients who did not receive NAC during 2011-2020. Results In the non-NAC group, the mean and median relative dose intensity (RDI) were 78.7% and 99.4%, respectively, and 11 patients (50%) had altered treatment schedules. The corresponding rates in the NAC group were 77.9% and 100%, respectively, and nine patients (45%) had altered treatment schedules, with no significant difference among the groups. Moreover, 17 patients (77.2%) in the non-NAC group and 16 patients (80.0%) in the NAC group continued S-1 treatment as planned for one year postoperatively, with no significant difference in the S-1 continuation rate (p = 0.500). Seventeen of 22 patients (77.3%) and 15 of 20 patients (75.0%) experienced several adverse events in the non-NAC and NAC groups, respectively. The frequency, severity, and type of adverse events were consistent among patients with and without NAC. Conclusions S-1 could be safely and continuously administered as adjuvant chemotherapy for patients with esophageal cancer regardless of NAC. Long-term prognosis should be evaluated for S-1 to become the standard treatment after esophagectomy.