ESTRO 2020 Abstract book

S131 ESTRO 2020

and ART (253 patients). RP was scored retrospectively according to CTCAEv3 and date of maximum RP grade was recorded. Differences in clinical, treatment-specific and dosimetric variables were compared with χ 2 tests (categorical variables) and Mann Whitney U tests (continuous variables). Cumulative incidences for RP grade 2 and above were compared with a log rank test. Results The incidence of RP grade 2 and above was reduced from 45.8% pre-ART to 18.2% ART, p<0.001 (Figure 1). There was no statistical significant difference in the prevalence of former or current smoking, COLD, sex, histology, age or FEV between the two groups. A decrease in median [range] GTV size from 56.7 [1.1;405.2] to 49.3 [3.3;1022.1]cm 3 was not significant, p=0.410. In the ART group, concomitant chemotherapy was more frequently applied (43.0% pre-ART vs 76.7% ART, p<0.001) and more patients were treated with 66Gy than with 50/60Gy (54.9% pre-ART vs 76.7% ART, p<0.001). However, following the introduction of ART, the PTV decreased significantly from 506.5 [70.6;1291.9] to 266.5 [30.6;1757.8]cm 3 , p<0.001. In combination with the increased use of IMRT (58.4 pre-ART vs 100% ART, p<0.001), mean doses to lung (16.9 [0.8;29.4]Gy pre-ART vs 12.1 [1.7;19.4]Gy ART, p<0.001) and heart (9.4 [0.1;39.7]Gy pre-ART vs 4.4 [0.1;33.9]Gy ART, p<0.001) also decreased significantly.

University Hospital, Department of Radiation Oncology, Homburg/Saar, Germany ; 3 University Hospital Mainz, Department of Radiation Oncology, Mainz, Germany ; 4 Kliniken Maria Hilf, Department of Radiation Oncology, Mönchengladbach, Germany ; 5 Marienhospital Stuttgart, Department of Radiation Oncology-, Stuttgart, Germany ; 6 Klinikum Mutterhaus der Boromäerinnen, Department of Radiation Oncology-, Trier, Germany ; 7 University Hospital Magdeburg, Department of Radiation Oncology, Magdeburg-, Germany ; 8 Charité University Hospital, Department of Radiation Oncology, Berlin, Germany ; 9 Offenburg St. Josefsklinik, Department of Radiation Oncology, Offenburg, Germany ; 10 Helios University Hospital Wuppertal, Department of Nuclear Medicine, Wuppertal, Germany ; 11 Marienhospital Stuttgart, Department of Nuclear Medicine, Stuttgart, Germany ; 12 University Hospital Mainz, Department of Nuclear Medicine, Mainz, Germany ; 13 Helios Kliniken Schwerin, Department of Nuclear Medicine, Schwerin, Germany ; 14 Saarland University Hospital, Department of Nuclear Medicine, Homburg/Saar, Germany ; 15 University of Mainz, Institute of Medical Biostatistics- Epidemiology and Informatics, Mainz, Germany ; 16 University of Freiburg, Institute for Medical Biometry and Statistics, Freiburg, Germany ; 17 University of Freiburg - Medical Center, Department of Radiation Oncology, Freiburg, Germany Purpose or Objective The PET-Plan prospective multicentre two-arm randomised trial (NCT00697333) investigated the optimization of concurrent radiochemotherapy (RT) planning using 18F-FDG-PET in locally advanced non small cell lung cancer (NSCLC). Here, we analyze the influence of protocol adherence and radiotherapy quality on outcome. Material and Methods Radiotherapy quality assurance (RTQA) as part of the PET- Plan study protocol included pro- and retrospective review of RT plans and RT application by predefined criteria. Medical and physical aspects were reviewed by radiation oncologists and medical physicists (RTQA group), as well as mutually by study center members. After passing the initial prospective central review of the first cases per study center, the site qualified for mutual review executed during study group meetings, where RTQA review results were discussed in teaching sessions in order to continually improve protocol compliance. After the end of recruitment, all cases again underwent post-treatment review by the RTQA group. Overall, up to 24 items per plan were reviewed and categorized into protocol compliant, minor, non-therapy relevant major (MA) and therapy-relevant (MA+) deviations. Those items comprised delineation of target volumes (GTV of the primary tumor, CTVs (involved nodal stations: CTVesc; elective lymph nodes: CTVel, only in study arm A)), delineation and adherence to dose constraints of organs at risk (OAR: lung, esophagus, spinal cord and heart), RT dose escalation and specifications and RT execution. Results Individual data of 204 randomized patients were analyzed (Arm A: n=99, B: n=105). Overall, 173 (75%) patients had any MA and 31 (19%) any MA+. Most commonly, MA and MA+ were observed for: CTV delineation, OAR delination of heart and spinal cord, OAR doses to lung and spinal cord, total dose of escalation volume (PTV) and overall treatment time. In low volume centers (≤ 5 patients) there was a tendency for more MA+. Median follow-up time was 29 months. Patients with MA+ had an inferior overall survival (HR 2.9 [95% CI 1.8–4.4], p<.001) as well as a higher risk of locoregional progression (HR 5.7 [95% CI 2.7– 11.1], p<.001) as compared to patients without MA+ deviations.There was an unfavorable impact on overall survival by incorrect OAR delination and disregard of OAR dose constraints (HR 3.6 [95%CI 1.5-7.3], p 0.006) as well

Conclusion After the introduction of ART, we observe a significantly lower incidence of grade 2-5 RP, compared to in the pre- ART period, despite increased use of high prescription doses and concomitant chemotherapy. Significant decrease of PTV size and more frequent use of IMRT treatment planning result in significantly lower lung and heart dose, while local control has been shown to improve [1]. [1] Tvilum, M, Khalil, A. Møller, D, Hoffmann, L, & Knap, M. (2015). Clinical outcome of image-guided adaptive radiotherapy in the treatment of lung cancer patients. Acta oncologica 54.1-8. OC-0231 Outcome impact of radiotherapy protocol compliance: RTQA results from the PET-Plan trial T. Schimek-Jasch 1 , S. Kremp 2 , M. Stockinger 3 , A. Küsters 4 , T. Hehr 5 , Y. Bultel 6 , P. Hass 7 , J. Fleckenstein 2 , A.H. Thieme 8 , S. Adebahr 1 , E. Gkika 1 , V. Duncker-Rohr 9 , M. Tosch 10 , S.M. Eschmann 11 , M. Miederer 12 , G. Holl 13 , H.C. Rischke 1 , A. Schaefer-Schuler 14 , J. König 15 , C. Broichhagen 16 , S. Lenz 16 , H. Binder 16 , A. Grosu 17 , U. Nestle 4 1 University of Freiburg- Medical Center, Department of Radiation Oncology, Freiburg, Germany ; 2 Saarland

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