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RESEARCH PRODUCT

The Impact of Radiotherapy Protocol Adherence on the Treatment Outcome in Patients With Locally Advanced NSCLC Treated With Concurrent Chemoradiation: Results From the Radiotherapy Quality Assurance of the International Randomized PET-Plan Trial

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PURPOSE/OBJECTIVE(S) The success of intensification and personalization of the curative treatment of non-small cell lung cancer (NSCLC) is strongly associated with the precision in radiotherapy (RT) treatment, which must therefore follow high standards. Herein we evaluate the impact of RT protocol adherence in the prospective international multicenter trial on curative treatment of NSCLC. MATERIALS/METHODS In the open-label, randomized, controlled PET-Plan trial, patients with inoperable NSCLC were randomized at a 1:1 ratio regarding the target volume delineation informed by ¹⁸F-FDG PET and CT plus elective nodal irradiation (Arm A) or target volumes informed by PET alone (Arm B) and received iso-toxically dose-escalated concurrent chemoradiation. The prospectively organized quality assurance program (RTQA) included individual case review by predefined criteria. 24 items (arm A) and 20 items (arm B) were scored as per protocol (pP), minor (miD), intermediate (inD) and major (maD) deviation by a multicenter panel of radiation oncologists and medical physicists. RESULTS Between 05/2009 and 11/2016, 205 patients were randomized, (one patient was excluded after randomization), 173 were treated per-RT protocol and 31 (15%) patients had maD. Patients with maD had an inferior overall survival (OS) (HR 2.9, 95% CI 1.8-4.4, P < .0001) as well as a higher risk of loco-regional progression (HR 5.7, 95% CI 2.7-11.1, P < .0001). Especially, patients with maD concerning normal tissue delineation and/or dose constraints had a worse OS (HR 3.6, 95% CI 1.5-7.3, P = 0.006) although there was no impact on the incidence of toxicities. Adjusting for the UICC stadium and the gross tumor volume as prognostic factors, the effects remained similar. CONCLUSION Non-adherence to the RT protocol was associated with an inferior OS and loco-regional control. These results underline the importance of RTQA.