ObjectivesExamine whether data from early access to medicines in the USA can be used to inform National Institute for Health and Care Excellence (NICE) health technology assessments (HTA) in oncology.DesignRetrospective cohort study.SettingOncology-based community and academic treatment centres in the USA.ParticipantsPatients present in a nationwide electronic health record (EHR)-derived deidentified database.InterventionsCancer drugs that underwent NICE technology appraisal (TA) between 2014 and 2019.Primary and secondary outcome measuresThe count and follow-up time of US patients, available in the EHR, who were exposed to cancer drugs of interest in the period between Food and Drug Administration (FDA) approval and dates relevant to the NICE appraisal process.ResultsIn 59 of 60 TAs analysed, the cancer therapy was approved in the USA before the final appraisal by NICE. The median time from FDA approval to the publication of NICE recommendations was 18.5 months, at which time the US EHR-derived database had, on average, 269 patients (SD=356) exposed to the new therapy, with a median of 75.3 person-years (IQR: 13.1–173) in time-at-risk. A case study generated evidence on real-world overall survival and treatment duration.ConclusionsAcross different cancer therapies, there was substantial variability in US real-world data accumulated between FDA approval and NICE decision milestones. The applicability of these data to generate evidence for HTA decision-making should be assessed on a case-by-case basis depending on the intended HTA use case.