Reduction in the Number of Chemotherapy Cycles in Combination With Pembrolizumab in First-line Treatment of PD-L1-positive Recurrent or Metastatic Head and Neck Squamous Cell Carcinomas

This study is testing whether reducing the number of chemotherapy cycles given alongside pembrolizumab (an immunotherapy) is just as effective as the standard number of cycles for treating head and neck squamous cell carcinoma (cancer of the mouth, throat, or voice box) that has returned or spread. **You may be eligible if...** - You are 18 or older with a confirmed diagnosis of recurrent or metastatic squamous cell carcinoma of the oropharynx, oral cavity, hypopharynx, or larynx - You have not received prior chemotherapy for metastatic or recurrent disease - Your tumor tests positive for PD-L1 (a marker that makes immunotherapy more likely to work) - You have measurable disease on CT or MRI scan **You may NOT be eligible if...** - You have cancer originating in the nasopharynx, sinuses, salivary glands, or skin - You previously received chemotherapy for metastatic disease - Your prior platinum chemotherapy for locally advanced disease ended less than 6 months ago - You have active autoimmune disease or are taking systemic steroids - You are pregnant or breastfeeding Talk to your doctor to see if this trial is right for you.