Nodal status of malignant lymphoma in pelvic and retroperitoneal lymphatic pathways: Comparison of integrated PET/CT with or without contrast enhancement

Aim: To determine the diagnostic accuracy of integrated contrast-enhanced positron emission tomography (PET) and computed tomography (CT), as compared with non-contrasted PET/CT, in evaluating nodal status of malignant lymphoma in pelvic and retroperitoneal lymphatic pathways. Materials and methods: Sixty-six patients (33 men and 33 women) with malignant lymphoma underwent staging with integrated CT and fluorine-18-fluorodeoxyglucose (¹⁸FDG) PET. Tumor types were diffuse large B-cell lymphoma (n = 26, 39%), follicular lymphoma (n = 20, 30%), Hodgkin disease (n = 16, 24%), and marginal zone B-cell lymphoma (n = 4, 6%). Both non-contrasted PET/CT and contrast-enhanced PET/CT images were examined separately by two different qualified physicians for each imaging modality, and nodal status of pelvic and retroperitoneal lymphatic pathways was evaluated. Reference standard included follow-up with clinical, laboratory, and conventional CT findings. We compared diagnostic accuracy retrospectively on basis of per-patient and per-lesion analyses between two modalities using McNemar test, respectively. Results: Nodal status of pelvic and retroperitoneal lymphatic pathways was more accurately determined on contrast-enhanced PET/CT (n = 52, 79%) compared with non-contrasted PET/CT (n = 47, 71%). Difference in the accuracy of nodal staging between non-contrasted PET/CT and contrast-enhanced PET/CT was significant (p = 0.048). On basis of per-lesion analysis, contrast-enhanced PET/CT determined more accurately the status of external iliac lymph node (p = 0.002), internal iliac lymph node (p < 0.0001), and common iliac lymph node (p = 0.002) compared with non-contrasted PET/CT. Diagnostic accuracies of paraaortic lymph node, aortocaval lymph node, and paracaval lymph node were similar by either non-contrasted PET/CT or contrast-enhanced PET/CT. Conclusion: Integrated contrast-enhanced PET/CT improves the diagnostic accuracy in evaluating nodal status of pelvic and retroperitoneal lymphatic pathways in patients with malignant lymphoma