[18F]-2-deoxy-D-glucose Positron emission tomography/computed tomography (18F-FDG PET/CT) is considered to be the current reference imaging technique nowadays for the management of the majority of lymphomas, particularly for HL and aggressive NHL. Revised Response Criteria (RRC) for malignant lymphoma recently incorporate 18F-FDG PET/CT evaluation in therapy response assessment. Lymphoma tissue is characterized also by altered tissue architecture consisting in higher cellularity and morphological changes of tumor cell and microenvironment. Magnetic Resonance (MR) represents the best imaging technique that allows the study of tissue ultra-structure. This study prospectively evaluated the WB-MR/DWIBS reliability, compared to 18F-FDG PET/CT, in the treatment response assessment of HL and aggressive-NHL, according to RRC for malignant lymphoma.
18 consecutive patients (9 male: 9 female, mean age of 48.9 years) with histologically proven lymphoma (11HL/7NHL) were enrolled. All patients were followed clinically throughout the study and evaluated by 18F-FDG PET/CT and WB-MR/DWIBS, within 10 days each other, before treatment start (staging) and at the end of the first line chemotherapy (re-staging). The RRC were used to assess tumor response, considering responders (R-group) and no-responders group (NR-group). Final clinical decision was made integrating therapy response according to the RRC and patient’s clinical status. Cohen’s K test was used to calculate the agreement between WB-MR/DWIBS and 18F-FDG PET/CT findings evaluating both nodal and extra-nodal involvement and distinguishing between HL and NHL. Using RRC we compared the classes of response with those obtained by replacing DWIBS with PET evaluation. Post-therapy WB-MR/DWIBS sensitivity, specificity, PPV and NPV were calculated in relation to the final clinical response as reference standard.
WB-MR/DWIBS and 18F-FDG-PET/CT showed a good agreement in NHL, in particular for nodal basins evaluation (K=0.937, 95%IC=0.814-1). By using WB-MR/DWIBS instead of 18F-FDG-PET/CT in the RRC, 4 NHL(57%) and 7 HL(64%) were placed into R-group and 3 NHL(43%) and 4 HL(36%) in NR-group. The agreement between the two diagnostic tools in the treatment response assessment by using RRC, was good in NHL (K=0.696, 95%IC=0.170-1), while quite low in HL (K=0.214, 95%IC=-0.377-0.806). Post-therapy WB-MR/DWIBS sensitivity, specificity, PPV and NPV were: 57%,73%,57.44% and 72.64%. Considering HL/NHL separately, they resulted 40%, 57.14%, 43.74 % and 53.34% in HL; while they were 100%, 80%, 66.67% and 100% in NHL.
18F-FDG PET/CT confirms its important role in therapy response evaluation of lymphoma patients, especially in HL. However WB-MR/DWIBS, although based on different physiological bases, may be complement to 18F-FDG PET/CT, improving the assessment of the chemotherapeutic effects especially in NHL or aggressive relapsing forms.