18f]PET-CT Scan Is Highly Accurate in Identifying Marrow Involvement of Diffuse Large B-Cell Lymphoma

Abstract

BACKGROUNDRecent advances in imaging and the use of prognostic indices and molecular profiling have improved our ability to characterize disease and predict outcomes in diffuse large B cell lymphoma (DLBCL). About 1/3rd of patients with DLBCL have bone marrow involvement (BMI) at the time of diagnosis, and bone marrow aspirate/biopsy (BMAB) is considered the gold standard to detect such involvement. [18F] fluorodeoxyglucose (FDG) positron emission tomography combined with computed tomography (PET-CT), has become a standard pre-treatment imaging in DLBCL and may be a noninvasive alternative to BMAB to ascertain BMI. Prior studies have suggested that PET-CT scan may obviate the need for BMAB as a component for staging patients with newly diagnosed DLBCL, but owing to a variety of reasons this is not yet a standard of practice. The aim of this retrospective study which included 99 patients with newly diagnosed de-novo DLBCL, who had undergone both BMAB and PET-CT, was to determine the accuracy of PET-CT in detecting BMI in DLBCL and define overall survival (OS) in these patients based on BMI by BMAB vs. PET-CT. METHODSThis study is a single institution retrospective review of patients' medical records. All patients with newly diagnosed DLBCL at Virginia Mason Medical Center between January 2004 to December 2013 who underwent pretreatment PET-CT and BMAB were included. PET-CT images were visually assessed for BMI including the posterior iliac crest. Patients with primary mediastinal DLBCL, previous history or co-existence of another lymphoma subtype and those with a non-diagnostic BMAB, and in whom the PET-CT did not show marrow signal abnormality were excluded from the analysis. Ann Arbor stage was determined using PET-CT with and without the contribution of BMAB, and the proportion of stage IV cases by each method was measured. RESULTS99 eligible patients were identified. The median age was 62 years (range, 24-88), 62 (59%) were male, 53 (50%) had elevated LDH and 17 (16%) had an ECOG performance status of >2. Thirteen (12%) patients had > 1 extra-nodal site of lymphoma involvement. R-IPI score was 1 in 39 (37%), 2 in 42 (40%), 3 in 20 (19%), and 4 in 4 (4%) patients. A total of 38 (36%) patients had BMI established by either PET-CT (n=24, 19%), BMAB (n=14, 13%), or both (n=12, 11%). 12 of the 24 patients (50%) with positive PET-CT had BMI by DLBCL, while only 2 of the 81 patients (2%) with negative PET-CT showed BMI. BMAB upstaged 1 of the 53 (2%) stage I/II patients to stage IV. The sensitivity of PET-CT scan to detect BMI by DLBCL was 86% while the specificity was 87%. 84 patients (85%) had concordant results between lymphomatous BMAB and PET-CT (12 patients were positive for both, and 72 patients were negative for both), but 15 patients (15%) had a discordant interpretation (3 patients were positive by BMAB and negative by PET-CT, and 12 patients were negative by BMAB and positive by PET-CT). PET-CT was highly accurate for detecting BMI at diagnosis in de-novo DLBCL. Although patients with positive BMAB patients had inferior 5 year OS estimates compared to negative BMAB (66% vs. 85%), no difference was demonstrated between PET-CT positive vs. PET- CT negative patients. (79% vs. 83%) (Table 1) CONCLUSIONSIn patients with newly diagnosed DLBCL, PET-CT is highly accurate in detecting BMI by lymphoma. In clinical practice, routine BMAB may no longer be necessary for all patients with DLBCL, who are staged by PET-CT, unless the results would change both staging and therapy. The prognostic implication of BMI identified by PET-CT compared to BMAB remains unknown. Whether a PET-CT precludes the need for a BMAB in patients with DLBCL remains to be evaluated in a prospective study. [Display omitted] DisclosuresNo relevant conflicts of interest to declare.