Drug Diffusion through Clinical Trial Sites: Evidence from Physician Prescribing of New Cancer Drugs
Clinical trials benefit patients directly by providing novel treatments, but little is known about the indirect effects of clinical trials on physician prescribing. In this study, we test whether exposure to a clinical trial of a new drug in a physician’s local geographic area affects the physician’s propensity to prescribe the drug. Utilizing the Medicare Part D prescribing patterns of more than 10,000 physicians across 29 new cancer drugs approved by the US Food and Drug Administration between 2014 and 2019, we find that exposure to clinical trials of new cancer drugs increases the likelihood that physicians prescribe these drugs by 0.18 percentage points, representing a 14% increase relative to the average prescribing rate. Notably, the effects are more pronounced for physicians graduating from higher-ranked medical schools, for more experienced physicians, and for physicians practicing in metropolitan areas. Further, our results suggest that the exposure to clinical trials reduces the physicians’ information acquisition cost of new cancer drugs. Specifically, the cost can be reduced by proximities to trial sites and to the first author of pivotal trial and by affiliation with trial sites.