Two cases of anal squamous cell carcinoma achieving complete response after docetaxel + cisplatin + S-1 (DCS) induction chemotherapy followed by chemoradiation

Anal squamous cell carcinoma (ASCC) is an uncommon tumor. However, its incidence is increasing worldwide. Surgical resection of locally advanced cases requires permanent anal prosthesis. Thus, chemoradiotherapy (CRT) is preferred as the first-line treatment; however, high local recurrence rate remains an issue. Here, we describe two cases of locally advanced ASCC treated with docetaxel + cisplatin + S-1 (DCS) followed by CRT with S-1 that showed complete response. The two patients, aged 69 and 65 years, were diagnosed with ASCC (cStage IIIB) at our hospital. Due to extensive lymph node metastases, the patients were treated with triple induction chemotherapy (DCS) followed by CRT with S-1. Positron emission tomography/computed tomography performed six months after starting the treatment showed disappearance of tumors, indicating a complete response. The patients continued to receive S-1 for one year and achieved relapse-free long-term survival since the completion of treatment. Therefore, induction chemotherapy with DCS, prior to CRT with S-1 may benefit patients with locally advanced ASCC.