Selection of mediastinal lymphoma patients for proton therapy in a prospective multi-institutional registry: Concordance with the ILROG guidelines.

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Conference Proceeding

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International Journal of Radiation Oncology Biology Physics


Purpose/Objective(s) Patients with mediastinal lymphoma are young and typically have curable disease. As such, advanced RT techniques such as proton therapy (PT) are often considered to minimize late toxicity. In 2018, ILROG published guidelines that identified 3 subsets of mediastinal lymphoma patients that may derive the greatest benefit from PT: patients with disease below the left main stem coronary artery, young females, and heavily pretreated patients. Within a prospective, multi-institutional PT registry of US community and academic institutions, we evaluated concordance between clinical practice and the ILROG guidelines in regard to patient selection for PT. Materials/Methods Patients eligible for analysis included those with lymphoma of the mediastinum treated exclusively with PT and had associated DICOM files. Given the challenge with reliably visualizing the left main stem coronary artery, the inferior-most aspect of the left pulmonary artery (PA) was used as a surrogate. Extent of disease was characterized as upper mediastinum (above level of left PA), middle mediastinum (below left PA but at or above the level of T8), or lower mediastinum (below T8). Disease extent was also characterized as whether it extended more than 3 cm below the carina. Results 56 patients treated between 11/2012 and 4/2019 with PT had DICOM data for review. All patients registered after 7/2017 had DICOM data for review. Median age at PT was 24 years (range, 12-88); 55.4% were female, 58.9% had stage I/II disease at initial diagnosis, and 85.7% were treated in the initial setting (versus relapsed/refractory). Histologies included Hodgkin lymphoma (78.6%), DLBCL (8.9%), PMBCL (8.9%), and other non-Hodgkin lymphoma (3.6%). Median RT dose was 30.6 Gy(RBE) (range, 19.5-54). Nearly all patients (54; 96.4%) met the ILROG inclusion criteria for consideration of PT to the mediastinum: 94.6% had disease below the left PA, 44.6% were young females (<35 >years) in whom PT could reduce breast dose, and 8.9% were heavily pretreated and at higher risk of RT-associated heart and lung toxicity. Nearly half fulfilled two (48.2%) or all three (3.6%) criteria. Two patients did not fulfill the criteria—both with exclusively upper mediastinal disease. Disease extent included the upper mediastinum (3.6%), middle mediastinum (48.2%), lower mediastinum (48.2%). In 94.6% of patients, disease extended 3 cm below the carina. For disease below the left PA, disease was anterior (94.6%), right (46.4%), left (41.1%), and posterior to the heart (23.2%). Conclusion Even prior to the ILROG guidelines, there was concordance among radiation oncologists regarding which mediastinal lymphoma patients may most benefit from PT. This most frequently included young patients with disease below the left PA for whom PT can reduce dose to the heart, lung, and breast tissue.





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