QA makes a clinical trial stronger: evidence-based medicine in radiation therapy.

Quality assurance (QA) for radiation therapy (RT) in clinical trials is necessary to ensure treatment is safely and effectively administered. QA assurance requires however substantial human and financial resources, as it has become more comprehensive and labor intensive in recent RT trials. It is presumed that RT deviations decrease therapeutic effectiveness of the studied regimen. This study assesses the impact of RT protocol-deviations on patient's outcome in prospective phase II-III RT trials. PubMed, Medline and Embase identified nine prospective RT trials detailing QA RT violation and patient's outcome. Planned QA analysis was preformed retrospectively and prospectively in eight and one studies, respectively. Non-adherence to protocol-specified RT requirements in prospective trials is frequent: the observed major deviation rates range from 11.8% to 48.0% (mean, 28.1 ± 17.9%). QA RT deviations had a significant impact on the primary study end-point in a majority (62.5%) of studies. The number of patients accrued per center was a significant predictive factor for RT deviations in the largest series. These QA data stemming from prospective clinical trials show undisputedly that non adherence to protocol-specified RT requirements is associated with reduced survival, local control and potentially increased toxicity.