Cancer Blood Tests Part 2: The clinical trial

About this episode

How do you decide whether a clinical trial “worked”? In Part 2 of our Galleri series, we examine the landmark randomized trial of a blood test designed to detect more than 50 cancers. We explore why different outcome measures led to dramatically different headlines, discuss primary versus secondary outcomes, pre-registration, hierarchical testing, and post hoc analyses, and explain why mortality remains the outcome everyone is waiting for. Along the way, we uncover a statistical mystery involving dozens of missing cancers and discover how a little arithmetic can sometimes reveal more than a press release. Statistical topics • cancer screening • exploratory analyses • hierarchical testing • missing data • multiple testing • outcome measures • post hoc analyses • pre-registration • primary and secondary outcomes • randomized clinical trials • screening tests Methodologic Morals • “When the simple numbers don't add up, pay attention. The arithmetic may be trying to tell you something.” • “The first question should not be, did it work? It should be, what counts as success?” References • Giridhar KV, et al. Safety and performance results from PATHFINDER 2, a registrational st