Treatment switching in oncology trials and the acceptability of adjustment methods.

Treatment switching has become an important issue in the development and approval of new drugs, particularly in oncology. Randomized controlled trials (RCTs) represent the gold standard for evaluating the effectiveness of interventions, but often patients randomized to the control group are permitted to switch onto the experimental treatment at some point during the trial. This is important, because standard statistical approaches used to analyze RCTs compare groups as randomized, based upon an intention-to-treat principle. When patients in both groups receive the new drug, such analyses do not provide an accurate estimate of the comparative effectiveness of the two treatments. This may lead to inappropriate decision-making - cost-effective drugs may not be approved. Limited healthcare finances may be used inefficiently. Health-related quality-of-life and lives may be lost.