The Analysis of Risk for Solitary Bone Plasmacytoma Rapidly Progressing to Multiple Myeloma
Authors: Chen Meilan , Li Juan 
Published: November 2021

Abstract
Background:
Solitary bone plasmacytoma(SBP) is a very rare and heterogeneous disease. Some patients have rapid progress into multiple myeloma. But some patients stay stable for a long time. Different patients have different clinical processes and prognostic performance. At present, there is no inconclusive prognostic factors of SBP progressed into multiple myeloma，and different studies have great different results. and they did not ues modern detection technology and methods. Therefore, there is no easy reliability methods for the factors of SBP progressed into multiple myeloma. There could not screen the SBP that rapidly progressing to MM and give intervention treatment for them.
Purpose:
to analyze the clinical characteristics and lesion biological markers of SBP patients using body PET / CT, flow cytometry and immunocellularization to and screen out the high-risk SBP patients who rapid progress into MM. SBP patients divided into different stratification according with high risk factors. And we preliminary establish the prognostic risk assessment systems which could predict SBP progressed into multiple myeloma.
Objects and methods:
Case: This study retrospectively analyzed 41 patients who were hospitalized from January 2003 to January 2020.All these patients accorded with the diagnostic standard of 2018 European solitary plasmacytoma .Enrolled 41 patients in groups. Observation indicators: age, gender, hemoglobin, β2 microglobulin, lactic acid dehydrogenase, blood calcium, creatinine,uninvolved immunoglobulin inhibited, M protein,X-ray / computed tomography (CT) / Magnetic Resonance Imaging(MRI) or whole body PET / CT, bone marrow smear, flow cytometry of bone marrow, the immunohistochemical conditions of the puncture lesion include VCAM-1, MMP9, VEGF, TGFβ, IGF-1, Ki-67, p53, CXCR4, 67LR, MCP-1, CCR2, CCR7.
Results:
1. General Characteristics: A total of 41 patients with SBP are enrolled in this study, The median age of onset is 53.02 years (20-73 years), and 22pts are males and 19pts females. The median follow-up time is 48 months, and during this time, 17 patients progressed into multiple myeloma.The median PFS is 84 months.For the significance of lesions, the lesions were in vertebral body of 16 cases (39.0%), 7 cases (17.1%), respectively in scapular, rib and clavicle. For treatment, 20 patients (48.8%) were received radiotherapy, 16 patients (39.0%) received surgery + radiotherapy, and 5 (12.2%) patients just only accepted surgery.Among 41 SBP, 17 patients(41.5%) progressed into MM during follow-up, including 8 cases (8/17)progressed within 1 year after diagnosis. 3 cases progressed between 1 to 2 years, and 3 cases between 2 to 4 years.Also 3 patients progressed above 4 years after diagnosis.
2. In single-factor and multi-factor analysis, the progress group and the disease stabilization group are independent adverse pre-factors affecting SBP progress into MM ,including the vertebral body (p =0.028), excition clone plasma cell in BM (p =0.010)and the proportion of ki67 positive cells&gt; 12.5%(p =0.019).
3. Establish formula model to predict the prognosis of SBP progressed into MM.On the base of beta Predicting prognosis = lesion is located in vertebral body × 2 +excited clone plasma cell in bone marrow × 3 + ki67 &gt; 12.5% × 4. According to the model, the score is between 0 points to 9 points, the scores &lt;2 are divided into low-risk group, and scores between 2 ~ 5 are divided into middle-risk group.When scores≥5 are divided into high-risk group. Among the 41 patients in this study, 15 patients (36.6%), are the low-risk group that PFS has not been achieved.And 11 patients (26.8%) are the middle-risk group ,which PFS is 8.3% of 2-year. Verify the prediction prognostic model of SBP progressed into MM. There are six cases of SBP which include the prognosisi factors can be used to verify our model in Guidong People's Hospital, Guangxi. These 6 patients are identical with our prognosis model.
Conclusions:
SBP patients divided into different stratification according with high risk factors. The vertebral body, excition clone plasma cell in BM and the proportion of Ki67 positive cells&gt; 12.5% are the independent adverse pre-factors for SBP progressed into MM. According the score of our model,SBP can be divided into low-risk, middle-risk groups and high-risk groups. It may require early intervention for high-risk patients that progressed into multiple myeloma within 2 years.

Disclosures
No relevant conflicts of interest to declare.