A proposed index of diffuse bone marrow [18F]-FDG uptake and PET skeletal patterns correlate with myeloma prognostic markers, plasma cell morphology, and response to therapy.

Abstract

The investigation of a semi-quantitative index in the pelvis to assess for diffuse bone marrow (BM) [18F]-FDG uptake and the investigation of PET skeletal patterns in multiple myeloma (MM) patients, in accordance with prognostic markers, clonal plasma cell (cPC) morphology, and response to therapy. We prospectively analyzed [18F]-FDG PET/CT in 90 MM patients (newly diagnosed, 60; relapsed/refractory, 30). Among other PET/CT parameters, we calculated the ratio SUVmax pelvis/liver and examined for correlations with known MM prognostic parameters, cPC morphology (good vs. low/intermediate differentiation), and response to therapy. SUVmax pelvis/liver ratio was significantly lower for the group of good differentiation vs. intermediate/low differentiation cPCs (p < 0.001) and showed a positive correlation with BM infiltration rate, β2 microglobulin, serum ferritin, international staging system (ISS), and revised ISS; no significant correlation was found with hemoglobin. A cutoff value of 1.1 showed an excellent specificity (99%) and high sensitivity (76%) for diffuse BM involvement (AUC 0.94; p < 0.001). Mixed pattern and appendicular involvement correlated with poor prognostic features while normal pattern, found in 30% of patients, correlated with good prognostic features. Presence of ≥ 10 focal lesions negatively predicted for overall response (p < 0.05; OR 4.8). The CT component improved the diagnostic performance of PET. This study showed, for the first time, that cPC morphology and markers related with MM biology, correlate with SUVmax pelvis/liver index, which could be used as a surrogate marker for BM assessment and disease prognosis; PET patterns correlate with MM prognostic features and response rates.