The Optimal Use of Imaging in Radiation Therapy for Lymphoma: Guidelines from the International Lymphoma Radiation Oncology Group (ILROG)

Abstract

Radiation therapy (RT) for the management of lymphoma has evolved over the past few decades. Large, extended, or involved fields have been replaced by smaller involved sites or nodal volumes. Currently, customized plans are created for each individual patient, and these plans encompass only the areas involved by disease. A critical factor that has enabled this shift in practice is the evolving use of imaging studies. Imaging plays a key role in patient selection and RT planning and delivery. The objective of this manuscript is to provide guidelines for best practice of use of imaging in pretreatment evaluation, treatment choice, RT target volume definition, and RT treatment verification and delivery.

Involved Site Radiation Therapy in Adult Lymphomas: An Overview of International Lymphoma Radiation Oncology Group Guidelines

“…Accurate contouring requires a thorough clinical assessment, high-quality imaging, and sometimes supplementary tests (eg, endoscopy). 5,16 18-Fluorodeoxyglucose (FDG) positron emission tomography (PET) is critical for accurate staging and may modify RT volumes. [17][18][19][20][21][22][23][24][25] PET does not obviate the need for contrast CT to delineate (for example) mediastinal lymphadenopathy, or magnetic resonance imaging (MRI) to define head and neck involvement.…”

“…Smallvolume disease not evident on PET may be visible on CT or MRI. 5,16 Imaging uncertainties may be due to the following factors (Fig. 1):…”

“…Heterogeneous FDG avidity. 5,18 C. Patient position and set-up Ideally, baseline imaging is performed in the intended treatment position to facilitate accurate image fusion. 4 This may not always occur.…”

“…First, small irradiated volumes require optimal imaging for accurate disease localization, as well as precise coregistration of baseline imaging information with the RT planning computed tomography (CT). 4,5 In practice, baseline imaging may be suboptimal or difficult to translate to the planning CT, owing to altered patient position or anatomic changes after chemotherapy. In 2014, the International Lymphoma Radiation Oncology Group (ILROG) introduced involved site radiation therapy (ISRT), a slightly larger volume intended to allow for these commonly encountered uncertainties.…”

Durable Complete Remission and Long-Term Survival in FDG-PET Staged Patients with Stage III Follicular Lymphoma, Treated with Wide-Field Radiation Therapy

“…Thirty patients had FDG-PET for response assessment, and all (100%) showed a complete metabolic response (CMR). These assessments pre-dated the adoption of the Deauville scale [37], and would be consistent with the Deauville responses of 1-2. In two cases, PET response was assessed after neoadjuvant systemic therapy, before RT.…”