Purpose: This phase II study investigated whether durvalumab/tremelimumab with proton therapy improves the objective response rate (ORR), overall survival (OS), and progression-free survival (PFS) in heavily treated recurrent or metastatic head and neck squamous cell carcinoma (HNSCC) patients.
Materials and methods: Patients who previously received more than one chemotherapy, including at least one platinum-based regimen, and who had at least two measurable lesions were enrolled. Patients received 1,500 mg durvalumab intravenously combined with 75 mg tremelimumab intravenously every 4 weeks for four cycles followed by 1,500 mg durvalumab every 4 weeks. After one cycle of the durvalumab/tremelimumab treatment, proton therapy was given with a total dose of 25 Gy in 5 Gy daily fractions to one of the measurable lesions. We also assessed the ORR in the target lesion outside the radiation field to evaluate the abscopal effect.
Results: Thirty-one patients were enrolled between March 2018 and July 2020. With 8.6 months of follow-up, the ORR was 22.6% (7/31), including one complete response and six partial responses. The median OS was 8.4 months (95% confidence interval [CI], 2.5 to 14.3) and the median PFS was 2.4 months (95% CI, 0.6 to 4.2). Among the 23 evaluable patients who completed proton therapy, the ORR was 30.4% (7/23). The median OS was 11.1 months (95% CI, 6.5 to 15.8), and the median PFS was 3.7 months (95% CI, 1.6 to 5.7). Grade 3 or higher adverse events were observed in six patients (19.4%) as follows: anemia (n=1), constipation (n=1), electrolyte imbalances (n=2), hyperglycemia (n=1), and pneumonia (n=1).
Conclusion: The combination of durvalumab/tremelimuab with proton therapy was tolerated well and had encouraging anti-tumor efficacy in non-irradiated tumor lesions of heavily treated HNSCC patients.
Keywords: Abscopal effect; Durvalumab; Immunotherapy; Proton therapy; Squamous cell carcinoma of head and neck; Tremelimumab.