Hodgkin Lymphoma: the Changing Role of Radiation Therapy in Early-Stage Disease—the Role of Functional Imaging

Early-stage classical Hodgkin lymphoma (CHL) is a highly curable malignancy. Historically, extended-field radiotherapy (EFRT) alone showed excellent cure rates, but the risk of radiotherapy (RT)-associated toxicities led to combined modality therapy (CMT) replacing RT alone. RT has subsequently evolved further with significant reductions of dose and field size, and is currently restricted to involved sites only (ISRT). Contemporary CMT yields cure rates in excess of 85 %, and most studies do not have adequate follow-up required to evaluate the risk reduction in late effects. In an effort to avoid RT altogether, response-adapted treatment approaches utilizing results of interim [18F]fluorodeoxyglucose (FDG) positron emission tomography with fused computed tomography (PET/CT) imaging have been studied. Results from two studies in favorable-risk (UK RAPID and EORTC H10F) and one in unfavorable-risk patients (EORTC H10U) suggest that omission of RT in patients with a negative interim PET/CT response (Deauville score ≤2) yields slightly inferior progression-free survival (PFS) compared to conventional CMT, but with no difference in overall survival (OS) albeit with short-term follow-up. In order to extrapolate results to daily practice, it is critical to understand the selection of patients entered on trials since definitions of favorable and unfavorable disease vary between study groups. Currently, CMT continues to be the standard of care for the vast majority of patients with early-stage CHL and RT is an integral part of therapy in patients with bulky disease. However, for selected patients with favorable characteristics, emerging data suggest that a chemotherapy-alone approach is reasonable.