A prospective, single-arm trial of PD-1 inhibitors plus chemoradiotherapy for solitary metachronous metastasis nasopharyngeal carcinoma

Purpose: Initial treatment for Recurrent/Metastatic Nasopharyngeal Carcinoma (R/M NPC) often involves Gemcitabine plus cisplatin with or without PD-1 inhibitors. However, PD-1 inhibitors' effectiveness varies, prompting for better treatments. This study explores effect and safety of combining PD-1 inhibitors with chemoradiotherapy for oligometastatic NPC patients. Methods: Oligometastatic NPC patients underwent radical treatment with PD-1 inhibitors and chemotherapy, followed by concurrent PD-1 inhibitors and chemoradiotherapy, and then maintenance PD-1 inhibitors. Objective response rate (ORR) and disease control rate (DCR) were calculated by irRECIST-1.1, and CTCAE-4.0 was used to evaluate the toxicity. Results: The study enrolled 47 patients with a median age of 46. The median follow-up lasted 16.5 months, with metastatic lesions receiving a median radiation dose of 45 Gy. The median courses of PD-1 inhibitors and chemotherapy were 9.5 and 5 respectively. The metastasis sites included lung (40.8 %), liver (21.1 %), mediastinal lymph node (7.9 %), abdominal lymph nodes (3.9 %), bone (21.1 %), adrenal gland (3.9 %), and brain (1.3 %). ORR and DCR were 85.1 % and 100 % at 3 months after radiotherapy. The median survival was not reached yet, and 1 and 2-year OS rates were 93.1 % and 78.4 %. The median PFS was 18 months, with 1 and 2year PFS rates of 70.2 % and 47.7 % respectively. PD-L1 expression showed a positive correlation for PFS. Twenty-five patients experienced grade 3 or 4 adverse events (AE) that were possibly related to chemotherapy. No grade 5 AE was observed. Conclusions: The synergy of concurrent PD-1 inhibitors and chemoradiotherapy shows promising efficacy and an acceptable toxicity for oligometastasis NPC patients.