Target Volume Delineation for Early-Stage Adult Hodgkin Lymphoma

Standard treatment for early-stage adult classic Hodgkin lymphoma (HL) is brief chemotherapy followed by involved site radiation therapy (ISRT). Effective chemotherapy has a high likelihood of eradicating initially microscopic disease. Hence, the clinical target volume (CTV) for ISRT includes only the tissue that contained macroscopic lymphoma before chemotherapy. With advanced 2-[18F]fluoro-2-deoxy-D-glucose (FDG)-positron emission tomography (PET)/computed tomography (CT) imaging, including image fusion and deep inspiration breath hold (DIBH) if possible, it is possible to contour this volume with high precision on the post-chemotherapy planning CT scan. With modern, highly conformal treatment techniques, this volume can be irradiated to the prescribed dose while maximally sparing the surrounding normal tissues. The rare subtype of nodular lymphocyte predominant Hodgkin lymphoma (NLPHL) has an indolent course and often presents with limited sites of involvement. If disease is localized, NLPHL in adults is treated with ISRT alone. In this situation, the CTV encompasses both the macroscopic lymphoma volume and adjacent lymph node areas that are at high risk of harboring microscopic disease, based on clinical judgment. No advantage is achieved with more extensive treatment fields, as were used in the past. Highly conformal RT techniques are used to irradiate this CTV while sparing surrounding normal tissues.