Efficacy and Safety of Re-Challenging PD-1 Inhibitors in Second-Line Treatment in Metastatic Nasopharyngeal Carcinoma Previously Treated with Chemotherapy and PD-1 Inhibitors

Background: We aim to evaluate the efficacy and safety of anti-PD1 rechallenge in combination with chemotherapy in patients with metastatic nasopharyngeal carcinoma (mNPC) who have progressed on prior anti-PD1 therapy. Patients and Methods: We enrolled patients with mNPC who received chemotherapy combined with PD-1 immune-checkpoint inhibitors (ICIs) or chemotherapy alone after prior progression of anti-PD1 therapy. The primary endpoint was progress-free survival (PFS), and the secondary endpoints included overall survival (OS), disease control rate (DCR) and objective response rate (ORR). Results: A total of 96 patients were eligible between January 2015 and December 2020. Thirty-seven (38.5%) were in the PD-1 ICIs re-challenge group, while the remaining 59 patients (61.5%) were in the chemotherapy group. The ORR and DCR of PD-1 ICIs group and chemotherapy group were 37.8% vs 23.7% and 86.5% vs.74.5%, respectively. After a median follow-up period of 21.1 months (IQR 16.1– 28.7), the log-rank analysis demonstrated a significantly improved PFS in the PD-1 ICIs re-challenge group compared to the chemotherapy group (8.4 months 95% CI 4.3– 14.0 vs 5.0 months 95% CI 2.8– 7.2, P = 0.03). However, no significant difference in OS was observed between the two groups (28.3 vs 24.1 months, P = 0.09). The two groups had similar adverse reactions, but the incidence of grade 3 or 4 thrombocytopenia was significantly higher in the PD-1 ICIs re-challenge group (18.9% vs 3.4%, P = 0.025). Conclusion: mNPC patients who progressed from prior anti-PD1 therapy could benefit from the anti-PD1 rechallenge in combination with chemotherapy. However, further validation is needed. Keywords: metastatic nasopharyngeal carcinoma, chemotherapy, PD-1 immune checkpoint inhibitors, second-line treatment strategies