Supplementary Text A1. Detailed search terms and steps in all databases

Supplement to the article "Efficacy and safety of PD-1 inhibitors in recurrent or metastatic nasopharyngeal carcinoma patients after failure of platinum-containing regimens: a systematic review and meta-analysis". <strong>Supplementary Text </strong><strong>A</strong><strong>1</strong><strong>.</strong><strong> Detailed search terms and steps in all databases</strong>