Exercise has long been hailed as cancer-fighting magic, but is there hard evidence behind the hype? In this episode, we tackle the CHALLENGE trial, a large phase III study of colon cancer patients that tested whether prescribed exercise could improve cancer-free survival. We translate clinical jargon into plain English, show why ratio statistics make splashy headlines while absolute differences tell the real story, and take a detour into why statisticians think survival analysis is downright sexy. And we even bring in a classic reality show to make sense of the numbers.
Statistical topics
- Data and Safety Monitoring Board (DSMB)
- Hazard ratios
- Intention-to-treat analysis
- Interim analyses
- Kaplan-Meier curves
- Phase III trials
- Randomized clinical trial
- Rates and rate ratios
- Relative vs absolute differences
- Stratified randomization with minimization
- Survival analysis
- Time-to-event variables
Methodological morals
- “Ratio statistics sell headlines. Absolute differences sell truth.”
- “Survival analysis is this sexy stats tool that makes every moment and every Cox count.”
References
- Courneya KS, Vardy JL, O'Callaghan CJ, et al. Structured Exercise after Adjuvant Chemotherapy for Colon Cancer. NEJM. 2025;393:13-25.
- Rabin RC. Are Marathons and Extreme Running Linked to Colon Cancer? The New York Times. Aug 19, 2025.
- Sainani KL. Introduction to survival analysis. PM&R. 2016; 8:580-85.
- Sainani KL. Making sense of intention-to-treat. PM&R. 2010;2:209-13.
Thanks
Thanks to Caitlin Goodrich for the episode topic tip!
Kristin and Regina’s online courses:
Demystifying Data: A Modern Approach to Statistical Understanding
Clinical Trials: Design, Strategy, and Analysis
Medical Statistics Certificate Program
Epidemiology and Clinical Research Graduate Certificate Program
Programs that we teach in:
Epidemiology and Clinical Research Graduate Certificate Program
Find us on:
Kristin - LinkedIn & Twitter/X
Regina - LinkedIn & ReginaNuzzo.com
- (00:00) - Intro
- (05:42) - Two different types of cancer studies
- (08:12) - Why might exercise affect cancer?
- (10:05) - Phase III trials are different
- (12:40) - Who was in the CHALLENGE trial?
- (13:31) - Stratified randomization with minimization
- (15:05) - The exercise prescription
- (19:17) - What did the CHALLENGE trial measure?
- (20:04) - Disease-free survival
- (21:59) - Data and Safety Monitoring Board – what do they do?
- (24:35) - Participants and adherence to exercise
- (26:54) - Intention-to-treat analysis
- (29:58) - Survival analysis overview
- (31:51) - Kaplan-Meier curves
- (34:27) - Reality-show analogy
- (36:54) - Ratio statistics are confusing
- (39:30) - Hazard ratios
- (47:03) - Wrap-up, rating, and methodological morals
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