PD-1 Inhibitors and Chemotherapy Combined with or without Radiotherapy for Patients with Oligometastatic Esophageal Cancer

Oligometastatic esophageal cancer (OMEC) is an intermediate state between local advanced and widespread metastatic disease, which is associated with better prognosis compared to poly-metastatic esophageal cancer (EC). The previous studies demonstrated the survival benefit from local radiotherapy for OMEC patients. But the data of PD-1 inhibitors combined with radiotherapy for OMEC is still scarce. The purpose of the present study was to determine the efficacy and safety of PD-1 inhibitors plus radiotherapy in OMEC.OMEC was defined as "up to five measurable metastatic lesions and up to three organs involved". Patients with OMEC receiving PD-1 inhibitors plus chemotherapy in a single center were retrospectively analyzed in this study. They were dichotomized according to whether or not they had received radiotherapy. The efficacy and safety of immunochemotherapy combined with radiotherapy (RT group) and immunochemotherapy alone (NRT group) were investigated.A total of 226 patients were included; 108 patients received PD-1 inhibitors plus chemotherapy and radiotherapy, while other 118 patients were treated with immunochemotherapy alone. Baseline characteristics were well balanced between the groups. The overall response rate (ORR) was 58.3% in the RT group and 41.5% in the NRT group (P = 0.012), respectively. The median PFS was 13.5 months (95% CI, 10.0-17.1) for the RT group and 8.8 months (95% CI, 9.2-12.0) for the NRT group (P = 0.000). The addition of radiotherapy was the major prognostic factor for PFS (hazard ratio, 0.56; 95% CI, 0.406-0.761; P = 0.000) by univariate Cox regression analysis. Patients were well-tolerated, and the overall incidence of adverse events was similar between the RT group and NRT group. In addition, the incidence of treatment-related pneumonitis did not differ between the two groups. Grade 3-5 pneumonitis was observed in 3.7% and 5.1% of patients in the RT and NRT groups, respectively.The additional of radiotherapy to PD-1 inhibitors and chemotherapy improved PFS of patients with OMEC and showed acceptable toxicity. Further prospective studies investigating the combination of immunochemotherapy and radiotherapy are warranted.