The advancement of therapeutic strategies in oncology such as precision oncology has generated significant interest in better estimating the response of modern phase I cancer clinical trials. These estimates have varied widely. In this commentary, we provide an umbrella review of phase I response rates and discuss methodological reasons for variation in prior estimates which include limited use of unpublished data, the inclusion of expansion cohorts that artificially raise response rates of cumulative response rates, varying enrolment of haematologic malignancies, and increased next in class drugs.
