Integrating whole-body metabolic tumor burden and serum biomarkers for comprehensive characterization of disease activity in patients with advanced multiple myeloma

Ziel/Aim:

Estimation of tumor load in multiple myeloma (MM) is challenging. The biomarker ß2 microglobulin (ß2M) is widely used to estimate myeloma cell mass and prognosis, but serum levels are influenced by a variety of factors such as varying secretion by myeloma cell clones and renal function. High serum levels of lactic dehydrogenase (LDH) have been shown to identify high-grade lymphoma-like myeloma. PET/CT is a useful tool for assessment of MM, particularly by identifying prognostically relevant, metabolically active disease.Aim of this study was to further characterize the association between whole-body metabolic tumor burden and serum markers in MM.

Methodik/Methods:

We retrospectively recruited 31 patients (55.7± 9.2 y) who had underwent whole-body FDG PET/CT (48 scans) for assessment of relapse or progressive disease after hematopoietic stem cell transplantation. Patients with at least one FDG-positive lesion were included. Metabolic tumor burden (MTV) was determined using an automatic segmentation algorithm (Rover ABX GmbH), and was tested for correlation with serum ß2M (primary hypothesis) as well as with LDH, albumin, creatinine, calcium and gamma globulin (explorative tests).

Ergebnisse/Results:

Median metabolic tumor burden was 71.4ml (range: 5-1318ml). ß2M did not demonstrate a significant correlation with metabolic tumor burden (Spearman rho=0.070, p=0.649). PET-defined myeloma burden was significantly correlated with LDH (rho=0.388, p=0.006). There was a tendency towards correlation with albumin (rho=-0.270, p=0.063). None of the other serum markers correlated with MTV.

Schlussfolgerungen/Conclusions:

PET-defined tumor burden provides incremental information over ß2M. FDG-uptake and ß2M define only partly overlapping measures of myeloma cell mass. PET may preferably identify high-grade lymphoma-like myeloma.