Selection of cohorts from Flatiron Health database
We used the following criteria to select advanced NSCLC Patients and advanced head and neck patients from Flatiron Health database16. 1) The patient should be >= 18 years of age at advanced diagnosis. 2) There should be some kind of activity (in drug administration or visit table) within 90 days of the advanced diagnosis. 3) The patient should have at least 1 record of systemic anti-cancer drugs 4) Exclude drug records that are part of clinical trials. This resulted in 4,784 NSCLC patients and 422 advanced head and neck cancer patients included in this study.The demographic profiles for these patients are described in Table S1 .