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Objective: To study the cytogenetic characteristics of extramedullary disease (EMD) in patients with multiple myeloma (MM) and their impact on prognosis. Methods: Patients with newly diagnosed MM (NDMM) at Peking Union Medical College Hospital (Beijing, China) between June 2007 and December 2019 were recruited for this study. Demographic information, clinical data, fluorescence in situ hybridization (FISH) results of marrow and tissue samples, and survival outcome data were collected. Results: A total of 439 patients with NDMM were divided into those without EMD (non‐EMD, n = 339), those with EMD with primary paraosseous plasmacytoma (pEMD‐B, n = 48), those with primary EMD with soft‐tissue involvement (pEMD‐S, n = 33), and those with secondary EMD (sEMD, n = 19). The incidence of EMD was 18.5% (81/439) at diagnosis and 22.8% (100/439) throughout the disease course. Comparison of FISH results showed a higher proportion of RB1 deletion (n = 20; 60.0% vs. 20.0%, p =.013) and MYC translocation (n = 12; 44.4% vs. 12.5%, p =.041) in the extramedullary tissues than in the paired bone marrow samples. At diagnosis, the percentage of MYC translocations in the sEMD group was notably higher than that in the non‐EMD group (55.6% vs. 15.5%, p =.012). The median overall survival (OS) of patients with pEMD‐S (32 months) and sEMD (17 months) was significantly shorter (both p =.001) than that of non‐EMD patients (60 months). Conclusion: Soft‐tissue EMD can be considered a high‐risk condition, even in the era of novel agents. MYC translocation can serve as a valuable marker that correlates with extramedullary spread and relapse in patients with MM and should be considered for inclusion in routine FISH panels in clinical practice. [ABSTRACT FROM AUTHOR]

Background: Myc rearrangement (Myc‐R) is a controversial factor linked to adverse outcomes in newly diagnosed multiple myeloma (NDMM). Aims: This study aimed to evaluate the impact of Myc‐R on the prognosis of NDMM patients and its role in risk stratification compared with traditional high‐risk cytogenetic abnormalities (HRCAs). Materials & Methods: A total of 417 NDMM patients enrolled from May 2009 to September 2022 were included. Fluorescence in situ hybridization (FISH) was used to detect Myc‐R and other Myc abnormalities (Myc‐OA). Median progression‐free survival (PFS) and overall survival (OS) were analyzed using Kaplan–Meier methods and log‐rank tests. Multivariate Cox regression analysis was used to identify independent risk factors. Results: Myc‐R was identified in 13.7% of patients, while 14.6% had Myc‐OA. Patients with Myc‐R had significantly shorter median PFS (15.9 months) and OS (25.1 months) compared with those with Myc‐OA (24.5 months PFS; 29.8 months OS) and Myc‐negative (Myc‐N) status (29.8 months PFS, 29.8 months OS). Myc‐R was independently associated with worse PFS and OS compared to Myc‐OA. Patients with Myc‐R alone had inferior median PFS (15.9 months vs. 28.1 months, p = 0.032) and OS (25.1 months vs. 61.2 months, p = 0.04) compared to those with traditional single HRCA. Discussion: The study suggests that traditional single HRCA may not significantly impact survival in NDMM patients. However, incorporating Myc rearrangement or traditional double/triple‐hit HRCAs into the risk stratification model improves its predictive value, highlighting the importance of Myc rearrangement in risk assessment. Conclusion: Myc rearrangement is an independent adverse prognostic factor in NDMM. The incorporation of Myc rearrangement or multiple HRCAs into risk stratification models improves their prognostic value, providing a novel perspective on high‐risk factors in NDMM. [ABSTRACT FROM AUTHOR]