157P Clinicopathological features of first primary myeloid sarcoma and the risk of multiple primary malignancies

Abstract

Myeloid sarcoma (MS) is a rare hematological malignancy with a reported incidence of 2.5-9.1%. In most cases, MS arises with Acute Myeloid Leukemia (AML) and only very few cases reported as a first primary MS. It is unclear if MS should be considered as a manifestation of hematological malignancy, or an independent malignancy. So this study aims to evaluate the clinicopathological features of myeloid sarcoma and assess the risk of developing multiple primary tumors to add an updated evidence to the literature and understand MS behavior for better management. Data of patients diagnosed with primary MS between 2000 and 2020 were obtained from the Surveillance, Epidemiology, and End Results (SEER) database. We used MP-SIR session with multiple outcome analysis to calculate the standardized incidence ratio (SIR), as observed/expected (O/E) and was considered significant if P<0.05, Excess Absolute Risk (EAR) per 10,000, and 95% confidence interval (CI). SPSS version 23 was used for data analysis. Out of 411 patients with primary MS, the mean age was 50 (SD=22.64). Subcutaneous primary MS was the most common (30%) followed by lymph nodes and gastrointestinal MS (17% and 10.5%). About 94 patients developed second primary malignancies with overall O/E of 7.93 (P<0.05, 95%CI: 0.0971%-0.0641%, EAR=533.2). About 60 patients (14%) with primary MS had high risk for developing developed Acute Non-Lymphocytic Leukemia (ANLL) (O/E=520.91 P<0.05, 95% CI=3.97%-6.7%, EAR=388.69) with increased risk in the interval 0-11 months (O/E=1697.27, P<0.05, 95%CI: 22.76-12.33, EAR=1488.97). About 13.3% of patients with primary MS developed AML with EAR of 356.31 (O/E=530.84, P<0.05%, 95%CI: 6.9-3.99) and 6 patients developed Non-Hodgkin Lymphoma (NHL) (O/E=11.77, P<0.05, 95%CI: 0.246-0.0432, EAR=35.63). MS is a very rare malignancy. This study showed difference in behavior of MS and first primary MS, with different presentation sites. Primary MS showed a significant risk of developing ANLL within the 0-11 months interval, most commonly AML, as well as a significant risk of developing NHL. This highlights the importance of screening for hematological malignancies once MS is diagnosed for early detection and better management.