Involved-node radiotherapy in early-stage Hodgkin's lymphoma

Radiotherapy of Hodgkin's lymphoma has evolved from extended-field to involved-field (IF) radiotherapy which reduces toxicity whilst maintaining high rates of healing. Recent publications recommend further reduction of the radiation field to involved-node (IN) radiotherapy; however, this concept has never been tested in a randomized trial. The German Hodgkin Study Group (GHSG) aims to compare IN with standard IF radiotherapy in the future HD17 trial. The clinical target volume (CTV) encompasses the initial volume of the lymph node(s) before chemotherapy and incorporates the initial location and extent of the disease, taking into account the displacement of the normal tissues. The margin of the planning target volume (PTV) should be 2 cm in the axial and 3 cm in the craniocaudal direction. To minimize lung and cardiac toxicity the target definition in the mediastinum is different. The concept of IN radiotherapy has been proposed as a means to further improve the therapeutic ratio by reducing the risk of radiation-induced toxicity, including second malignancies. Field sizes will further decrease compared to IF radiotherapy.