Prognostic value of [18F]FDG-PET/CT in multiple myeloma patients before and after allogeneic hematopoietic cell transplantation

Despite improved treatment options, multiple myeloma (MM) remains an incurable disease. The aim of this study was to investigate the prognostic value of positron emission tomography/computed tomography (PET/CT) using F-18-2'-deoxy-2'-fluorodeoxyglucose ([F-18]FDG) in MM patients shortly before and similar to 100 days after allogeneic hematopoietic cell transplantation (allo-HCT). In this retrospective analysis, we evaluated [F-18]FDG-PET/CT-scans of 45 heavily pre-treated MM patients before and 27 patients after scheduled allo-HCT. All scans were qualitatively and semi-quantitatively assessed for the presence of active disease. Serological response was recorded according to International Myeloma Working Group (IMWG) criteria. Progression-free (PFS) and overall survival (OS) were correlated with different PET/CT-derived parameters, such as presence, number and maximum standardized uptake value (SUVmax) of focal myeloma lesions. The impact of extramedullary disease on patient outcome was also assessed. PET/CT negativity -prior to or following allo-HCT- was a favorable prognostic factor for progression-free and overall survival (both, PFS and OS: pre-HSCT p < 0.001, post-HCT p < 0.005). High FDG-uptake (SUVmax > 6.5) revealed a significantly shortened survival compared to patients with a lower SUVmax (< 6.5) (OS, 5.0 +/- 1.1 m vs. not reached - longest 122.0 m; p < 0.001). Moreover, our data prove that a higher number (> 3) of focal lesions (pre-HCT: both PFS and OS: p < 0.001; post-HCT PFS: p < 0.001, OS: p = 0.139) as well as the presence of extramedullary disease serve as adverse prognostic factors prior to and after allo-HCT. At response assessment after allo-HCT, [F-18]FDG-PET/CT had a complementary value in prognostication in addition to IMWG criteria alone. [F-18]FDG-PET/CT before and shortly after allogeneic HCT is a powerful predictor for progression-free and overall survival in MM patients.