Abstract P057

Proton therapy for limited stage classical Hodgkin lymphoma patients (PRO-Hodgkin): an interim analysis of clinical outcome.

Background: Most patients with limited stage classical Hodgkin lymphoma are cured with a short course of chemotherapy followed by radiotherapy (RT). Patients treated with RT are at risk of late side effects, particularly cardiovascular disease and second cancer. Proton therapy (PT) can reduce dose to organs at risk due to the finite range of the protons. This is a second interim analysis of the non-randomized PRO-Hodgkin study.

Methods: Since 2019, 53 patients with supradiaphragmal disease were treated with involved node/site PT with pencil beam scanning (PBS). Twenty-five patients not suitable for PT received photon therapy and were followed for comparison. Treatment was 2-4 cycles of ABVD followed by a dose of 20 Gy (RBE)/10 fractions to patients without risk factors and 29.75 Gy (RBE)/17 fractions to patients with risk factors. The median age was 32 (18-60) years. Forty-two (79%) patients were in stage IIA, 10 (19%) IA and 1 (2%) IB. All patients with mediastinal disease were treated in deep inspiration breath hold and mostly with two anterior oblique fields. Treatment plans were robustly optimized. All patients had a back-up photon plan.

Results: All patients were in complete remission (CR) after PT and none has died or relapsed at a median follow-up of 19 months from the end of therapy. Acute toxicity was generally limited apart from skin reaction in 34 (64%) patients. It was of grade 1 in 32 and grade 2-3 in 2 patients. Two patients suffered from pneumonitis grade 2 where symptoms declined after initiation of steroids (table 1). Five patients experienced an unforeseen neurological adverse event (AE), manifested as a hyperesthesia and/or burning sensation from the skin in a dermatomal pattern with onset two weeks to five months after end of radiotherapy. The symptoms were transient and so far, no patient has developed any long-term sequelae. However, the study was temporarily paused for investigation of the neurological AEs and during this period the eligible patients were treated with photon therapy. Some patients have also been treated with photon therapy due to dosimetric and technical reasons and due to patients choice.

Conclusion: PBS PT for Hodgkin lymphoma patients is well tolerated with good local control. Skin reaction was seen in a most patients and transient neurological AE and pneumonitis in a few. Dosimetric comparison between photon- and proton therapy plans will be analysed to evaluate which patients benefit the most from RT.

Authors

Christina Goldkuhl, Anna Bäck, Gunilla Enblad, Ingrid Glimelius, Lotta Hansson, Urban Jerlström, Ann-Sofie Johansson, Jenny Kahlmeter-Brandell, Johan Linderoth, Marzia Palma, Daniel Molin