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.

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Background and purposeIntensity-modulated radiotherapy (IMRT) credentialing for a EORTC study was performed using an anthropomorphic head phantom from the Radiological Physics Center (RPC; RPCPH). Institutions were retrospectively requested to irradiate their institutional phantom (INSTPH) using the same treatment plan in the framework of a Virtual Phantom Project (VPP) for IMRT credentialing.Materials and methodsCT data set of the institutional phantom and measured 2D dose matrices were requested from centers and sent to a dedicated secure EORTC uploader. Data from the RPCPH and INSTPH were thereafter centrally analyzed and inter-compared by the QA team using commercially available software (RIT; ver.5.2; Colorado Springs, USA).ResultsEighteen institutions participated to the VPP. The measurements of 6 (33%) institutions could not be analyzed centrally. All other centers passed both the VPP and the RPC ±7%/4 mm credentialing criteria. At the 5%/5 mm gamma criteria (90% of pixels passing), 11(92%) as compared to 12 (100%) centers pass the credentialing process with RPCPH and INSTPH (p = 0.29), respectively. The corresponding pass rate for the 3%/3 mm gamma criteria (90% of pixels passing) was 2 (17%) and 9 (75%; p = 0.01), respectively.ConclusionsIMRT dosimetry gamma evaluations in a single plane for a H&N prospective trial using the INSTPH measurements showed agreement at the gamma index criteria of ±5%/5 mm (90% of pixels passing) for a small number of VPP measurements. Using more stringent, criteria, the RPCPH and INSTPH comparison showed disagreement. More data is warranted and urgently required within the framework of prospective studies.

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