A phase 2 clinical study of nimotuzumab plus S-1 and concurrent radiotherapy in 75 years and older patients with esophageal squamous cell carcinoma.

4027 Background: Concurrent chemoradiotherapy is the standard treatment method for inoperable and locally advanced esophageal cancer. Nevertheless, due to decreased physical function and the presence of multiple complications, older patients often have reduced tolerance to radiotherapy and chemotherapy. Methods: We conducted this prospective, single-center, phase II study to evaluate the efficacy and safety of nimotuzumab (an epidermal growth factor receptor antibody) plus concurrent radiotherapy and S-1 in 75 years and older patients with stage II-IVB esophageal squamous cell carcinoma (ESCC). The primary endpoint was progression-free survival (PFS). The secondary endpoints were overall survival (OS), objective response rate (ORR), disease control rate (DCR), safety, nutritional indicators, and quality of life (QOL). Most nutritional indicators remained stable after treatment. Results: As of June 2024, a total of 56 patients were enrolled in this study. The median follow-up was 24.1 months (95% CI: 8.8, 34.1). 11 patients had complete response, 39 patients had partial response, 5 patients had stable disease, and 1 patient had progressive disease. The ORR was 89.2%, and the DCR was 98.1%. The 1- and 3-year PFS rates were 67.8% (95% CI: 55.5%, 80.1%) and 35.8% (95% CI: 17.6%, 54.0%), with the median PFS was 25.3 months (95% CI: 16.5, 34.1). The 1- and 3-year OS rates were 79.6% (95% CI: 68.8%, 90.4%) and 40.1% (95% CI: 21.1%, 59.1%), with the median OS was 28.2 months (95% CI: 24.1, 32.3). Most adverse events were grade 1-2 (85.7%). Among survivors, 45.5% patients reported high satisfaction with their QOL, and 84.8% patients did not experience weight loss. Conclusions: Our treatment combination of nimotuzumab plus S-1 and concurrent radiotherapy indicated favorable efficacy and safety profile. This might be an underlying treatment choice for older patients with ESCC. Clinical trial information: NCT06048913 .