Abstract P097

The status quo of involved-field radiotherapy – Quality analysis of radiotherapy in the GHSG HD 16

Question: The HD 16 trial of the German Hodgkin Study Group (GHSG) investigated the use of consolidative radiotherapy (RT) after 2 cycles of ABVD chemotherapy for early-stage Hodgkin lymphoma (HL) and could demonstrate the superiority of a combined modality approach [1]. The present work aims at analyzing the quality of involved-field RT used in this study.

Methods/Material:
For quality assessment, 100 randomly chosen plans from the HD 16 trial were requested and analyzed. RT was assessed by experts of the radiation therapy panel of the GHSG using initial (staging) imaging, RT plans and the recommendation forms by the reference radiation oncology. Evaluation was graded as „correct“, „minor deviation“ or „major deviation“. Statistical analyses were performed using SPSS (version 27/28, IBM, NY, USA).

Results: Radiation doses were adequate with a median of 20 Gy (19.8 Gy-21.6 Gy) in normofractionation. In the majority of radiation series, supradiaphragmatic target volumes were treated (91 %), with the regions most commonly irradiated being supraclavicular left/right (73 % each), infraclavicular left/right (73 % each) and cervical left/right (44 % and 45 %, respectively). Acute treatment toxicities were mild to moderate with only 3 cases of grade 3-4 toxicities (1 nausea/vomiting, 1 dysphagia, 1 mucositis). According to the RT panel, 84 % of cases were evaluated as „correct“, 5 % as „minor deviations“ and 11 % as „major deviations“. Major deviations were caused by insufficient dose coverage of involved regions in most cases (10/11), predominantly in the upper mediastinum (5/10 cases). Previous GHSG studies in early-stage HL (HD 10 [2] and HD 13 [3]) showed lower rates of RT series according to protocol (38.8 % and 52 %, respectively). A χ2-test was used to compare the number of correct RT series in the different GHSG study generations (HD 13 vs. HD 16). No expected cell frequencies were below 5. Results reveal a significant improvement in favor of HD 16 (χ2(1)=33.8, p<0.001 φ= -0.247). Similar outcomes were found for the association of GHSG study generation and the absence of major deviations (χ2(1)=27.4, p<0.001 φ=- 0.222).

Conclusion: Since its introduction in HD10, involved-field RT has evolved considerably. However, continuous efforts in RT quality assurance and training are needed in the modern era.

Literature: 1 JCO. November 2019; 37(31):2835-2845. 2 IJROBP. August 2008; 71 (5):1419-1424. 3 SUON. February 2017;193(2):109-115.

Authors

Michael Oertel, Dominik Hering, Christopher Kittel, Nina Nacke, Kai Kröger, Jan Kriz, Michael Fuchs, Christian Baues, Dirk Vordermark, Rita Engenhart-Cabillic, Klaus Herfarth, Peter Lukas, Heinz Schmidberger, Simone Marnitz, Peter Borchmann, Uwe Haverkamp, Andreas Engert, Hans Theodor Eich