Proton beam therapy for mediastinal Hodgkin lymphoma: A prospective study of clinical efficacy and safety

Abstract

Background: Proton beam therapy using pencil beam scanning is an advanced radiotherapy technique that utilises proton beams to precisely target tumours. It is known for its enhanced ability in sparing healthy tissue and potentially reducing toxicity. Clinical experience with pencil beam scanning in the treatment of mediastinal Hodgkin lymphoma remains limited.

Patients and methods: This study aimed to evaluate the toxicity and outcomes of a prospectively observed cohort. A total of 162 patients were irradiated between May 2013 and December 2020, with a median age of 32 years (range: 18.4-79.2) and followed up until April 2024. The median applied dose was 30 GyE (range: 20-40). Deep inspiration breath hold was used in 146 patients to enhance targeting precision.

Results: The disease-free survival, overall survival and local control rates were 95.1 %, 98.8 % and 98.8 %, respectively. The median follow-up was 59.1 months (range: 4-120.1). The most common acute toxicities observed were oesophageal and skin toxicity. Grade 1 oesophageal mucositis occurred in 76 patients (47 %), grade 2 in 16 patients (10 %). Dermatitis of grade 1 and 2 was observed in 65 (40 %) and 4 (3 %) patients respectively. Grade 1 pulmonary toxicity presented in 8 patients (4.9 %), and grade 2 in one patient (0.6 %). The most predominant late toxicity was grade 2 hypothyroidism in 37 patients (23 %). Three patients (1.8 %) underwent coronary interventions during follow-up, and one patient was diagnosed with hepatocellular carcinoma 3 months post-RT. No unexpected acute or late toxicities were observed.

Conclusion: Proton beam therapy using pencil beam scanning is a safe and effective technique in terms of toxicity and local control, even when irradiating mediastinal targets.

Keywords: Deep inspiration breath hold; Mediastinal Hodgkin lymphoma; Pencil beam scanning; Proton beam radiotherapy; Radiation oncology.