P-225: Risk Factors and Prognosis of Extramedullary Disease in Newly-Diagnosed Multiple Myeloma Patients

Introduction: Extramedullary Disease (EMD) in Multiple Myeloma (MM) is detected in 4-7% of patients at the time of diagnosis and increases to 6-20% in relapsed/refractory patients. The prognosis of extramedullary involvement in myeloma is quite poor. In our retrospective study, we aimed to determine the risk factors for EMD, to investigate the relationship between bone marrow (BM) fibrosis and EMD, and the effects of BM fibrosis on survival in newly diagnosed MM patients presenting with EMD at the time of diagnosis.

Methods: A total of 189 MM patients who were newly diagnosed between November 2016 and September 2023 were included in the present study. EMD is defined as soft tissue plasmacytomas that occur due to hematogenous spread and have no contact with bone structures.

Results: EMD was detected in 21 (11.1%) of the 189 patients who were included in the present study. A significant relationship was detected between the median White Blood Cell Count (WBC) at diagnosis and the presence of fibrosis in the BM in the univariate analysis of factors that might affect the presence of EMD. In multivariate analysis, the median WBC count at diagnosis (OR 1.15, 95% CI 1.03-1.28, p=0.015) and the presence of fibrosis in the BM (OR 3.45, 95% CI 1.09-10.89, p=0.032) were found to be independent risk factors for EMD. After a median follow-up period of 36 months, the median overall survival (OS) in patients with EMD was 13 months, and the median OS in those without extramedullary involvement was 77 months (HR: 3.09, 95% CI 1.52-6.26, p = 0.002). No difference in OS was observed between patients with BM fibrosis (Grade 1-3) and patients without fibrosis (HR:1.04, 95% CI 0.60-1.79, p=0.885).

		Non-Extramedullary Disease (n=168)	Extramedullary Disease (n=21)	P value
Age (Median)	Years	64.5 (40-86)	67 (37-78)	0.849
Gender	Male	103 (61.3%)	12 (57.1%)	0.712
	Female	65 (38.7%)	9 (42.9%)
WBC	x109/L	6.1 (1.6-26)	8.4 (3-20)	0.013
LDH	U/L	189 (60-1210)	208 (160-540)	0.123
Albumin	g/dl	3.5 (1.8-5.2)	3.5 (2.4-4.4)	0.829
β2Microglobulin	mg/L	5.6 (1.1-55)	5.7 (2.2-30)	0.538
Type of M protein	IgG Non-IgG	102 (60.7%) 66 (39.3%)	14 (66.7%) 7 (33.3%)	0.475
Revised-International Staging System (R-ISS)	I II III	29 (17.3%) 116 (69 %) 23 (13.7%)	5 (23.8%) 11 (52.4%) 5 (23.8%)	0.839
High Risk Cytogenetics*	Yes	18 (10.7%)	2 (9.5%)	0.801
Bone Marrow Plasma Cell Percentage		50 % (10-90)	45 %(10-80)	0.805
Bone Marrow Fibrosis (Grade I-III)	No Yes	77 (45.8%) 91 (54.2%)	4 (19%) 17(%81%)	0.019

Conclusions: As a result of the present study, it was found that BM fibrosis might be a predictive factor for the presence of EMD. A detailed examination for EMD might be required in newly diagnosed MM patients in case of BM fibrosis. We think that it will contribute to the improvement of prognosis, especially if the definition of EMD is standardized, risk factors are determined fully with prospective studies with a larger number of patients, and treatment standardization is identified.