Radiotherapy plus camrelizumab and irinotecan for oligometastatic esophageal squamous cell carcinoma patients after first-line immunotherapy plus chemotherapy failure: An open-label, single-arm, phase II trial

Abstract

Background and purpose: Immunotherapy has revolutionized the treatment of advanced and metastatic esophageal squamous cell carcinoma (ESCC), but most patients eventually developed disease progression. Immuno-resistance is becoming an unavoidable clinical problem. Oligometastasis is a limited-metastatic state, and patients at this stage should be evaluated for the addition of metastasis-directed local intervention, which may be associated with improved prognosis. As an immunomodulator, radiotherapy may exhibit synergistic effect when added to immunotherapy. This study assessed the efficacy and safety of low-dose radiotherapy plus immunotherapy and second-line chemotherapy in oligometastatic ESCC.

Materials and methods: In this phase II trial (ChiCTR2000040533), oligometastatic ESCC patients after first-line immunotherapy plus chemotherapy failure were treated with low dose radiotherapy plus camrelizumab and second-line irinotecan chemotherapy. The primary endpoint was progression-free survival (PFS). Secondary endpoints were overall survival (OS), objective response rate (ORR), disease control rate (DCR), clinical benefit rate (CBR), and safety. Abscopal response rate (ARR) and abscopal control rate (ACR) were also been explored.

Results: Between November 19, 2018 and March 17, 2021, 49 patients were enrolled. With a median follow-up of 12.8 months, median PFS and OS were 6.9 months (95%CI, 4.6-9.3) and 12.8 months (95%CI, 10.1-15.5), respectively. ORR was 40.8% (95%CI, 27.3-55.7). DCR was 75.5% (95%CI, 60.8-86.2). ARR was 34.7% (95%CI, 22.1-49.7). ACR was 69.4% (95%CI, 54.4-81.3). The most common adverse effects of any grade were myelosuppression, weight loss and fatigue. Grade 3 or 4 treatment-related adverse events occurred in 31 (63.3%) patients, with the most common being leukopenia (30.6%). No treatment-related deaths occurred.

Conclusion: Low dose radiotherapy plus camrelizumab and irinotecan exhibited survival benefit with manageable safety for oligometastatic ESCC patients after first-line immunotherapy plus chemotherapy failure. It deserves to be validated in a larger trial.

Keywords: Chemotherapy; Esophageal squamous cell carcinoma; Immunotherapy; Oligometastases; Radiotherapy.