Advanced topics in evidence-based urological oncology: using results of a subgroup analysis

Randomized, controlled trials are the cornerstone of evaluation for therapies in urologic oncology. Clinicians and investigators are frequently interested in whether treatment effects differ among subgroups of patients defined by clinically relevant characteristics.

The evidence-based approach to subgroup analysis is explored using an example from the urologic literature. Potential reasons why the results of subgroup analyses may not be reliable are reviewed. Criteria for assessing the validity of a subgroup effect are described.

The likelihood of observing clinically important differences in treatment results by chance increases with each additional comparison of groups. Ideally, subgroup comparisons should be specified a priori and few in number. The probability of observing the difference in outcomes due to chance should be low and, ideally, the difference will be large. Finally, external evidence or biologic data should support the hypothesized difference in subgroup outcomes.

Use of these criteria for subgroup analyses will promote a more evidence-based management for oncologic diseases within urology. Understanding appropriate use of subgroup analyses will help clinicians target therapies towards those patients most likely to benefit, and avoid both limiting potentially beneficial therapies or utilizing ineffective therapies when observed subgroup treatment effects are likely due to chance.