The role of initial 18F-FDG PET/CT in the management of patients with suspected extramedullary plasmocytoma

Background: Extramedullary plasmacytoma (EMP) is a plasma cell malignancy that originates in soft tissues without evidence of systemic spread, and its management differs from other plasma cell neoplasms. The purpose of the present study was to evaluate the role of initial F-18-FDG PET/CT in the management of patients with clinical suspected EMP. Methods: F-18-FDG PET/CT scans performed in 21 patients (M/F = 12/9, mean age 51.1 +/- 15.3 years) with clear suspicion of EMP from 2006 to 2015 were analysed retrospectively. The detection of new lesions and the change in treatment were evaluated. Results: PET/CT detected new lesions in 38.1% (8/21) of patients with 17 lesions, and lymph nodes were the most common site, accounting for 70.6% (12/17) of all lesions, followed by bone (n = 2), and less frequently, breast (n = 1), lung (n = 1), and stomach (n = 1). These findings resulted in treatment changes in 7 patients with EMP. Among these, 4 patients had major treatment changes and 3 patients had minor changes. Of the 21 patients, progression to MM was observed in 8 patients (8/21, 38.1%). In univariate analysis, tumour size > 4 cm and partial response (PR) after treatment were significant prognostic factors for Progression-free survival (PFS). Conclusions: Our data indicated that F-18-FDG PET/CT is helpful in the detection of additional lesions throughout the body, including lymph node involvement and distant additional lesion, which may have resulted in treatment change.