In multiple myeloma (MM), malignant plasma cells infiltrate the bone marrow. In some cases, plasma cells migrate out of the bone marrow creating either para-skeletal plasmacytomas (PS) or infiltrating soft tissues as extramedullary plasmacytomas (EMD). The aim of this study was to define risk groups in newly diagnosed MM (NDMM) patients with PS and EMD plasmacytomas. In total, 523 NDMM patients with PS plasmacytomas and 196 NDMM patients with EMD plasmacytomas were diagnosed in the Czech Republic between 2004 and 2021 using modern imaging methods. Patients’ data were analyzed from the Registry of Monoclonal Gammopathies of the Czech Myeloma Group. In NDMM patients with PS plasmacytomas, we found a subgroup with <5% of bone-marrow plasma cells to have the best prognosis (mPFS: 58.3 months (95% CI: 33.0−NA); mOS: not reached). The subgroup with >5% of bone-marrow plasma cells and ≥3 plasmacytomas had the worst prognosis (mPFS: 19.3 months (95% CI: 13.4−28.8), p < 0.001; mOS: 27.9 months (95% CI: 19.3−67.8), p < 0.001). Our results show association between tumor burden and prognosis of NDMM patients with plasmacytomas. In the case of PS plasmacytomas, NDMM patients with low BM PC infiltration have an excellent prognosis.

• Keywords
• multiple myeloma, plasmacytomas, risk factors, survival,
• Publication type
• Journal Article MeSH

Multiple myeloma (MM) is characterized by malignant plasma cell infiltration of the bone marrow. In extramedullary multiple myeloma (EMD), a subclone of these cells migrates out of the bone marrow. Out of 4 985 MM patients diagnosed between 2005 and 2017 in the Czech Republic, we analyzed 234 secondary EMD patients to clarify risk factors of secondary EMD development. We found younger age [<65 years; odds ratio (OR) 4·38, 95% confidence interval (CI): 2·46-7·80, P < 0·0001], high lactate dehydrogenase (LDH) levels (>5 μkat/l; OR 2·07, 95% CI: 1·51-2·84, P < 0·0001), extensive osteolytic activity (OR 2·21, 95% CI: 1·54-3·15, P < 0·001), and immunoglobulin A (IgA; OR 1·53, 95% CI: 1·11-2·11, P = 0·009) or the non-secretory type of MM (OR 2·83; 95% CI: 1·32-6·04, P = 0·007) at the time of MM diagnosis to be the main risk factors for secondary EMD development. Newly diagnosed MM (NDMM) patients with subsequent EMD had inferior median progression-free (PFS) and overall (OS) survival when compared to NDMM patients without future EMD [mPFS: 13·8 months (95% CI: 11·4-16·3) vs 18·8 months (95% CI: 17·7-19·9), P = 0·006; mOS: 26·7 months (95% CI: 18·1-35·4) vs 58·7 months (95% CI: 54·8-62·6), P < 0·001]. We found that NDMM patients with specific risk factors associated with secondary EMD development have a more aggressive disease course before secondary EMD develops.

• Keywords
• extramedullary disease, multiple myeloma, prognostic factors,
• MeSH
• Survival Analysis MeSH
• Humans MeSH
• Multiple Myeloma mortality   physiopathology   MeSH
• Prognosis MeSH
• Retrospective Studies MeSH
• Risk Factors MeSH
• Aged MeSH
• Check Tag
• Humans MeSH
• Male MeSH
• Aged MeSH
• Female MeSH
• Publication type
• Journal Article MeSH
• Research Support, Non-U.S. Gov't MeSH