Quality Assurance of Dose-Escalated Radiation Therapy in a Randomized Trial for Locally Advanced Oesophageal cancer

Abstract

The ongoing phase 2/3 PRODIGE 26/CONCORDE trial compares chemoradiation therapy with and without dose escalation in patients with locally advanced or unresectable esophageal cancer. The results of a benchmark case procedure are reported here to evaluate the protocol compliance of participating centers as part of quality assurance for radiation therapy. Volume delineation, target coverage, and dose constraints to the organs at risk (OARs) were assessed on treatment plans of a common benchmark case performed by each participating center. The centers were classified in 3 categories: per protocol, minor acceptable deviation (MiD), or major unacceptable deviation (MaD). A plan was rejected if ≥4 MiDs or 1 MaD were found. Thirty-5 centers submitted 43 plans. Among them, 14 (32.6%) were per protocol, 19 (44.2%) presented at least 1 MiD, 2 (4.6%) presented at least 1 MaD, and 8 (18.6%) presented both MiD and MaD. Overall, 11 (25.6%) plans were rejected. Only 1 plan was rejected because gross tumor volume was not correctly delineated. The OAR delineation was respected in all cases. Dose constraints to the OARs were respected in the majority of cases except for the heart, where one-third of the plans presented a deviation. As for the target volume, 3 plans (5.8%) had a major underdosage and 1 plan (1.9%) had a major overdosage. Overall, 58% of all treatments were planned with intensity modulated radiation therapy, whereas 42% were planned with 3-dimensional chemoradiation therapy. Significantly more plans in the intensity modulated radiation therapy group were accepted compared with the 3-dimensional chemoradiation therapy group (P = .03). The high frequency of protocol deviations underlines the importance of a quality assurance program in clinical trials. Further work should assess the impact of quality assurance for radiation therapy on patient outcomes.