Favorable efficacy of S‐1 treatment for locoregionally advanced cutaneous squamous cell carcinoma in the head and neck region

Abstract

AbstractCutaneous squamous cell carcinoma is usually treated with surgery; however, locoregionally advanced cutaneous squamous cell carcinoma can be difficult to resect. Although recent guidelines from Western countries recommend using anti–programmed cell death protein 1 (PD‐1) antibodies, including cemiplimab and pembrolizumab, there are no approved anti–PD‐1 antibodies for locoregional cutaneous squamous cell carcinoma in Asian countries. S‐1 is an oral drug with a low incidence of severe toxicity that can be used for head and neck cancers, including head and neck locoregional cutaneous squamous cell carcinoma, in Japan. We retrospectively evaluated patients with head and neck locoregional cutaneous squamous cell carcinoma treated with S‐1 at two Japanese institutions (2008–2022). The initial dosage was determined by the body surface area (<1.25 m2: 80 mg/day, 1.25–1.5 m2: 100 mg/day, ≥1.5 m2: 120 mg/day) for 28 consecutive days. The outcome measures were objective response rate (ORR), progression‐free survival (PFS), and overall survival (OS). Fourteen patients were included. The ORR was 78%, and the complete response (CR) rate was 64.3%. The median PFS and OS were not reached (NR) (95% confidence interval [CI], 5.9 months–NR) and NR (95% CI, 13.8 months–NR), respectively. The 12‐month PFS and OS rates were 51% and 85%, respectively. Six of the nine patients who achieved CR showed no recurrence during the follow‐up period (median follow‐up, 24.7 months). After CR, three patients experienced recurrence. Among these, two resumed S‐1 treatment and subsequently underwent salvage surgery, resulting in a sustained absence of recurrence. One patient developed lung metastasis and died, although S‐1 therapy was resumed. Only one patient (7.1%) developed grade 3 anemia. S‐1 showed favorable efficacy and low toxicity in patients with head and neck locoregionally advanced cutaneous squamous cell carcinoma. S‐1 may be a good alternative to the anti–PD‐1 antibody for treating head and neck locoregionally advanced squamous cell carcinoma.