Current Situation of Proton Therapy for Hodgkin Lymphoma: From Expectations to Evidence

SIMPLE SUMMARY: Hodgkin lymphoma (HL) is a highly curable disease; in this context, the limitation of late adverse events is of prime importance for the patient. Proton therapy for mediastinal HL irradiation theoretically limits secondary cancer excess risk and should reduce late toxicities compared with classical radiation therapy techniques. However, due to the limited clinical experience, strong evidence is still lacking to support proton therapy in HL management despite excellent tolerance. In addition, randomized controlled trials are probably unrealistic in this context. National and international registries may be useful to strengthen support for HL proton therapy. ABSTRACT: Consolidative radiation therapy (RT) is of prime importance for early-stage Hodgkin lymphoma (HL) management since it significantly increases progression-free survival (PFS). Nevertheless, first-generation techniques, relying on large irradiation fields, delivered significant radiation doses to critical organs-at-risk (OARs, such as the heart, to the lung or the breasts) when treating mediastinal HL; consequently, secondary cancers, and cardiac and lung toxicity were substantially increased. Fortunately, HL RT has drastically evolved and, nowadays, state-of-the-art RT techniques efficiently spare critical organs-at-risks without altering local control or overall survival. Recently, proton therapy has been evaluated for mediastinal HL treatment, due to its possibility to significantly reduce integral dose to OARs, which is expected to limit second neoplasm risk and reduce late toxicity. Nevertheless, clinical experience for this recent technique is still limited worldwide. Based on current literature, this critical review aims to examine the current practice of proton therapy for mediastinal HL irradiation.