Skeletal Involvement in Advanced Stage Lymphomas: Role of Total Body Magnetic Resonance.

Introduction: Skeletal localizations is reported in approximately 10–20% of cases of advanced stage malignant lymphomas. Detection of osseous involvement can change clinical stage and consequently determine the choice of treatment. Computed tomography (CT) is considered the gold standard for lymphoma staging and evaluation of treatment response; this technique, however, has a limited sensitivity in identifying extra-nodal disease, especially skeletal localizations. Positron emission tomography (PET) using fluorine-18 (FDG) has a higher sensitivity in recognizing bone involvement and is now a well-recognized diagnostic tool, complementary to CT. Total body magnetic resonance (MR) may rapresent a useful technique for detection and better characterization of tumoral bone lesions. In this report total body MR is compared with conventional imaging procedures (CT and PET) in the evaluation of Hodgkin (HL) and non Hodgkin lymphomas (NHL) with suspected skeletal involvement.

Patients and methods: In the last year, 4 patients with diagnosis of HL, and 8 patients with diffuse large B cell lymphoma, with clinical signs or radiological findings suggesting skeletal involvement, underwent total body MR in addiction to standard staging techniques (CT and PET). All patients showed at diagnosis a systemic disease with nodal involvement. Total body MR was performed with a body coil (1.5 Tesla) and images were obtained by using fast spin-echo (FSE) short time inversion recovery (STIR) and spin-echo single-shot (SE-EPI-SSH) sequences diffusion weighted. MR was performed at diagnosis in 6 cases, at restaging in 4 cases and in two cases both at the onset and after treatment, for a total of 14 examinations. MR images were compared with those obtained from conventional imaging performed at the same time.

Results: At diagnosis a total of 8 MR were performed, and multifocal skeletal involvement was detected in all cases. On the contrast, CT was negative in 6/8 cases, showing a lower sensitivity (25% vs. 100%); moreover, when positive (2/8 cases), CT detected a lower number of osseous localizations. PET was performed at diagnosis in 5 patients and resulted positive in 4 cases, identifying a minor extension of osseous involvement. At restaging 6 MR were performed: in 4 cases no skeletal lesions were detected, accordingly to CT and PET results, confirming the complete remission obtained after treatment. In the remaining two patients MR was persistently positive at restaging. PET showed a concordant result in one of these two cases, but detected less sites of involvement.

Discussion: These data suggest that total body MR may play a role in investigating patients affected by malignant lymphoma with suspected skeletal involvement. FSE-STIR and SE-EPI-SSH sequences diffusion weighted can accurately detect and characterize the hyper-intensity of lymphoma bone lesions. On the contrary, CT sensitivity was very low for skeletal involvement (25%); it derives that this technique alone is unable to correctly evaluate disease extension, possibly resulting in patients under-treatment. PET findings regarding skeletal involvement are often concordant with total body MR, but a lower number of bone lesions is detected in the majority of cases.