Evidence for external beam radiotherapy in mediastinal Hodgkin and non-Hodgkin lymphoma - systematic review.

Introduction and objective: Proton beam therapy (PBT) provides the opportunity for a more localized delivery of high energy protons and may reduce the damage to healthy tissues and vital organs. The aim of this review was to assess the effects of proton therapy for patients diagnosed with Hodgkin or non-Hodgkin lymphoma treated with mediastinal irradiation.

Review methods: A systematic search of EMBASE, MEDLINE via OVID and Cochrane Library was conducted in May 2022 according to PRISMA guidelines to identify relevant data on the efficacy and toxicity of proton beam therapy for patients diagnosed with Hodgkin or non-Hodgkin lymphoma.

Brief description of the state of knowledge: Of 566 screened abstracts (430 after de-duplication) 11 studies with a total of 529 patients were included. All studies were case series published between 2011-2021. Median range of follow-up time was 15-63.6 months. The overall survival (OS) for 2 years varied from 91% - 98% for 5 of the included studies. Three of the included studies had favourable outcomes with 2-year progression-free survival (PFS) ranging from 73% - 94%. Skin reaction, oesophagitis and fatigue were found to be the most common grade 1 and grade 2 toxicities. No acute or late grade 4 and higher toxicities/adverse events were observed.

Summary: There are data indicating that PBT may to be an effective treatment against mediastinal Hodgkin and non-Hodgkin lymphoma. Because all the studies were case series, the authors of this review have little confidence in the evidence. There remains a need for well-designed randomized controlled trials to inform about the optimal approach to proton irradiation in HL and NHL.