Efficacy of Chemotherapy After Immune Checkpoint Inhibitor Discontinuation in Head and Neck Cancer

Objective: Immune checkpoint inhibitors (ICI) have become widely used becuse of their effectiveness and relatively low rate of severe adverse events. However, active treatment should be continued after discontinuation of ICI as response rates are lower than that of conventional cytotoxic chemotherapy. The purpose of the present study was to determine the efficacy of treatment after ICI discontinuation. Methods: This was a retrospective study from hospital charts of 99 consecutive cases treated with ICI at our facility since 2017. Of these, 79 cases of squamous cell carcinoma which had already discontinued ICI were enrolled in the present study. Results: After discontinuation of ICI, 40 cases received active treatment with salvage chemotherapy (SCTx; 33 cases) or surgery or radiotherapy (seven patients) and 39 cases received nonactive treatment. SCTx comprising paclitaxel and cetuximab (PTX-Cmab) was administered to 15 cases and other SCTx regimens to 18 cases. A significant increase in overall survival (OS) was observed with active treatment compared with nonactive treatment. No significant differences in OS or progression-free survival (PFS) were observed between SCTx regimens; however, there was a trend toward increased survival with PTX-Cmab. Univariate analysis of overall response rate (ORR) demonstrated significant differences in the site of disease at ICI and SCTx regimens. A significant difference in disease control rate was observed between SCTx regimens. Multivariate analysis of ORR demonstrated a significant correlation with PTX-Cmab treatment. Conclusion: Active treatment after ICI discontinuation and the use of PTX-Cmab as SCTx may increase OS in head and neck squamous cell carcinoma.