Abstract P085

Definition of a risk collective for high cardiac radiation doses - A post-hoc analysis of the HD17 study by the German Hodgkin Study Group reference radiation oncology panel

Background: Radiotherapy (RT) is an essential part of modern treatment strategies for Hodgkin lymphoma (HL). However, efficacy has to be careful weighted against putative toxicity. Identifying those patients with high cardiac radiation exposure prior to RT may be a valuable strategy to guide optimization or even omit RT in favor of a chemotherapy-only treatment. We analyzed patients with a high RT dose to the heart within the patient collective of the HD17 study, as a modern study for intermediate-stage HL.

Methods: Overall, 176 patients (134 with involved-node RT) were analyzed by the reference radiation oncology panel as part of the study’s quality assurance. The present analysis focusses on patients exceeding dose recommendatios given by the International Lymphoma Radiation Oncology Group. Dosimetric and toxicity data were taken from the radiation plans and documentation by the study central.

Results: From the 176 patients evaluated, 139 had a mediastinal involvement, 43 of whom had a mean heart exposure >15 Gy, defined as a threshold for RT plan optimization (mean: 19.8 Gy). Of these 43 patients, the majority had stage II disease (91 %), no B-symptoms (86 %) and was <50 years of age (86 %). Disease spread to both the upper (95 %) and lower (98 %) mediastinum in most cases. Except for the mediastinum, the most prevalent regions were supraclavicular right/left (63 %/77 %) and infraclavicular right/left (61 %/72 %). Concerning GHSG risk factors, mediastinal bulk, extranodal spread, involvment of > 3 lymph node areas and elevated ESR were seen in 47 %, 16 %, 61 % and 35 %, respectively. In comparison to patients with lower heart doses, bulky disease and extranodal spread were seen more frequently in patients with increased heart dose (p=0.043 and p=0.035, respectively). This was in contrast to an elevated ESR (p=0.058), > 3 areas (p=0.552), stage II HL (p=0.722) as well as involvment of the left axilla, lower or upper mediastinum (p=1.0).

Conclusion: Pre-chemotherapy risk factors may be suitable predictors for RT dose exposure and can help to identify patients at higher risk for long-term toxicity. Further analysis on the influence of partial mediastinal involvement as well as modern RT techniques will broaden the perspective.