Hounsfield units from unenhanced 18F-FDG-PET/CT are useful in evaluating supradiaphragmatic lymph nodes in children and adolescents with classical Hodgkin’s lymphoma

Abstract

Background. The precise identification of the primarily-affected nodal regions in Hodgkin’s lymphoma (HL) is essential in determining the stage of the disease and the intensity of chemotherapy and radiotherapy. Objectives. The aim of this study was to use the degree of X-ray attenuation (XRA) in Hounsfield units (HU) and the lymph node-to-muscle attenuation ratio (LN/M) in computed tomography (CT) unenhanced imaging, routinely performed with 18F-fluorodeoxyglucose positron emission tomography (18F-FDG-PET), to distinguish HL-affected supradiaphragmatic lymph nodes. Material and methods. The study included 52 patients with classical HL treated according to the EuroNet-PHL-C1 protocol. Patients received 2 chemotherapy cycles after 18F-FDG-PET/CT testing, followed by re-examination. The lymph nodes were evaluated according to the Society for Pediatric Oncology and Hematology’s GPOH-HD-2002 study and Lugano criteria as not-involved (NI-LN) and involved (I-LN). Results. A significant difference (p < 0.001) was found in the XRA and LN/M values between NI-LN and I-LN before treatment and after the 2 chemotherapy cycles. The optimal cut-off point for XRA (44.7 HU) and LN/M (0.79) values distinguishing I-LN from NI-LN nodes was determined by receiver operating characteristic (ROC) analysis. After 2 cycles of chemotherapy, higher XRA (p = 0.002) and LN/M (p = 0.001) values in the group with inadequate early CTx response were found. Conclusions. The use of XRA in HU and LN/M, together with the existing standard, can improve the qualification of supradiaphragmatic lymph nodes in HL.