Diagnostic and prognostic use of FDG-PET scans in Waldenstrom's macroglobulinemia

Abstract

e19518 Background: Waldenstrom's macroglobulinemia (WM) is a rare lymphoplasmacytic lymphoma. More sensitive tools of tumor burden and prognosis are needed in these patients (pts). The use of FDG-PET has not been previously studied in WM but has proved an effective diagnostic and prognostic tool effective in low-grade lymphomas. Therefore the objective of this study was to determine whether FDG-PET was an effective tool in evaluating pts with WM. Methods: We included all pts enrolled on a prospective phase II clinical trial of bortezomib and rituximab for pts with upfront or relapsed/refractory (RR) WM. All pts were CD20 positive with histologically confirmed disease and underwent staging evaluation by FDG-PET in combination with CT scan before and after therapy. Patients received 6 cycles of bortezomib IV weekly at 1.6mg/m2 on days 1, 8, 15q28 and rituximab at 375 mg/m2 on days 1, 8, 15 and 22 in cycles 1 and 4. Correlation was made with the international prognostic scoring system for WM and monoclonal protein response rate. Results: 53 pts were included, of which 35 were RR and 18 pts were upfront. Median age was 63 years (range 42–81), 64% were male. Before therapy, 34 pts (64.2%) had positive FDG-PET findings with a median IgM of 2825, Beta 2 microglobulin of 3.6, and Age of 61. 36 pts showed a minor response or greater with a correlation to negative PETs after therapy. Conclusions: Over 60% of WM pts demonstrated FDG-avid disease when using FDG-PET scans, with the majority showing negative disease after therapy. This correlates with the 67.9% response rate. Positive PET images were inversely correlated to IgM level and directly related to elevated Beta-2 microglobulin and age. Significantly PET positive individuals may demonstrate a poorer prognosis. FDG-PET scans may prove an effective tool in the diagnosis and prognosis in WM. [Table: see text]