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

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) unenhancedimaging, 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, followedby re-examination. The lymph nodes were evaluated according to the Society for Pediatric Oncology andHematology'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 andI-LN before treatment and after the 2 chemotherapy cycles. The optimal cut-off point for XRA (44.7 HU) andLN/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 thegroup 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 qualificationof supradiaphragmatic lymph nodes in HL.