Comparison of metabolic activity in mantle cell lymphoma at biospy site and other tumor sites using 18F-FDG PET

Abstract

18529 Background: Mantle cell lymphoma (MCL) is a mature B-cell non-Hodgkin’s lymphoma (NHL) with a variable clinical course ranging from indolent to aggressive. Treatment for MCL is complicated by this variability, as systemic chemotherapy for NHL is directed by the aggressiveness of the lymphoma. Previous attempts have been made to correlate clinical outcome in MCL with histologic features. More recently, measurement of metabolic activity using 18F-fluorodeoxyglucose-positron emission tomography (FDG-PET) was found to be highly correlative with the aggressiveness of NHL. Given the clinical heterogeneity of MCL, the search for the true metabolic status in MCL is important in prognostication and management. We propose to study the metabolic activity in MCL by comparing the maximum SUV at the site of biopsy with the highest SUV in other MCL areas of the body. Methods: 12 patients with newly diagnosed MCL and having staging by FDG-PET were identified. PET(CT) body scans were obtained in the usual fashion. The SUVs, defined as tumor activity divided by dose injected per lean body mass, from the PET and PET-CT cameras were cross validated to produce the same value in a given phantom and patient. Maximum biopsy SUV was measured by searching the maximum value within a volume of interest over the known biopsy site, and highest body SUV was similarly searched in known tumor sites in other body areas. Results: One patient was excluded because the tumor at the biopsy site had been completely resected. The remaining 11 patients (M:F=8:3, age=63±8 yrs) were analyzed. The SUV at biopsy sites ranged from 2.1 to 9.8 (mean=5.2±2.3). The SUV in other tumor sites ranged from 4.8 to 18.6 (mean=8.9±4.1), which was significantly higher when compared to the respective biopsy site (p=0.0036). Conclusions: As the SUV of MCL at the biopsy site may not represent the highest SUV, it is important to search other tumor sites in the body for the highest SUV to help in grading, managing, and subsequent monitoring of MCL. Perhaps FDG-PET can direct biopsies to tumor sites with the highest SUV and subsequently provide useful histologic detail for predicting clinical course. Future study is needed to correlate the maximal SUV of MCL with histology and clinical course. No significant financial relationships to disclose.