Global Head and Neck Cancer Market Assessment, By Therapy Type [Chemotherapy, Immunotherapy, Targeted Therapy] By Route of Administration [Injectable, Oral], By Drug Class [EGFR Inhibitors, Mitotic Inhibitors, Anti-PD-1 Monoclonal Antibodies, Others], By Distribution Channel [Retail and Specialty Pharmacies, Hospital Pharmacies, Online Pharmacies] By Region, Opportunities and Forecast, 2017-2031F