Molecular and Whole-body MR Imaging in Lymphomas

Overview

Lymphomas are classified as Hodgkin's or non-Hodgkin's lymphomas, of which especially the latter represent a heterogeneous group with varying patterns of prognosis, biological behaviour and response to treatment. 18F-FDG PET/CT is useful for staging and response monitoring but has the disadvantage of associated radiation exposure which may not be desirable for young patients. Advanced MRI techniques including diffusion weighted imaging (DWI) are increasingly used for improved lesion detection and characterisation of lymphomas and in the whole-body mode offer a promising radiation-free alternative to CT. Molecular imaging in turn is important in theranostics medicine where detection of therapeutic target is essential. The concept of theranostics has been successfully adapted to management of neuroendocrine tumors (NET) where peptide receptor radiotherapy (PRRT) is offered to patients progressing on treatment with long-acting somatostatin analogues. Recently in the investigator's hospital a case of diffuse large B-cell lymphoma (DLBCL) was initially misdiagnosed as NET because of high uptake of 68Ga-DOTANOC in pancreatic tumor at PET/CT. A PubMed search revealed a similar case report in bronchial tumor which turned out to be DLBCL (Jain et al. Clin Nucl Med 2014;39:358-359). Bearing these two cases in mind the investigators now aim to systematically study somatostatin receptor status (ssr) by measuring uptake of 68Ga-DOTANOC with PET/CT in patients with newly diagnosed non-Hodgkin's and Hodgkin's lymphoma. The imaging findings will be compared to immunohistochemically determined ssr-subtypes 2,3 and 5 obtained from pre-treatment fresh tumor samples and 18F-FDG PET/CT which is part of standard diagnostic evaluation. Furthermore, whole-body MRI with DWI will be performed before, during and after chemotherapy to define the most sensitive and specific imaging method appropriate for routine diagnosis and follow-up. This study has potential implications for future response monitoring and follow-up imaging techniques in patients with malignant lymphoma and provides additional biologic characterization which may be useful for novel therapeutic approaches such as PRRT.

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