Gurney, Mark E.

Abstract Background: 'Myelodysplastic syndrome (MDS) with isolated del(5q),' as defined by the World Health Organization (WHO) criteria (SwederlowSH, et al, 2008) is a unique pathological entity with favorable outcomes. The 2016 revision to the classification expands this entity to include cases that have an additional cytogenetic abnormality, with the exception of monosomy 7 or del(7q) (Arber DA, et al, Blood 2016). The objective of our study was to evaluate the prognostic impact of an additional cytogenetic abnormality, other than monosomy 7 or del(7q), in patients with 'MDS with isolated del(5q)'. Methods: After due IRB approval, the Mayo Clinic MDS database (n=1067) was utilized for this study. All patients had bone marrow (BM) biopsies and cytogenetic studies performed at diagnosis. The International Society for Cytogenetic Nomenclature guidelines were used for cytogenetic nomenclature, while the 2008 and 2016 WHO criteria were used for morphological diagnosis. Results: Patient Characteristics: 72 patients (7.2%) met the 2016 WHO criteria for 'MDS with isolated del(5q)' of which 60% were female and median age was 74 years (28-90). In 61 (85%) cases del(5q) was the only cytogenetic abnormality, while in 11 (15%), del(5q) was present with an 'additional cytogenetic abnormality' (ACA). One additional case within the database had del(5q) accompanied with monosomy 7, which was not included in the analysis. Risk stratification by IPSS-R was as follows; 24 (29%) 'very low', 44 (64%) 'low' and 4 (6%) 'Intermediate' risk, with no patient classified as 'high' or 'very high' risk. At a median follow up of 43 months, 55 (76%) deaths and 5 (7%) leukemic transformations were documented. del(5q) versus del(5q) with an additional cytogenetic abnormality- phenotypic correlates: In the 'del(5q) with ACA' group, the additional abnormalities included trisomy 8 (n=4), del(20q) (n=3), der(9;18) (n=1), inv(3)(p25,q21)(n=1), -Y (n=1), and i(Xp) (n=1) (Table 1). There was no significant difference between the 'del(5q)' and 'del(5q) with ACA' groups in terms of age, gender, hemoglobin, platelet count, white cell count, absolute neutrophil count, bone marrow blast percentage or transfusion requirement. A greater proportion of the 'del(5q) with ACA' group (27%) had IPSS-R risk in the 'intermediate' category compared to the 'del(5q)' group (2%) (p=0.01). 18 of 42 cases diagnosed after 2004 (43%) were treated with lenalidomide, with no difference in the proportions treated between the two groups (p=1.00). del(5q) versus del(5q) with an additional cytogenetic abnormality- impact on overall survival (OS) and leukemia-free survival (LFS): The median survival of the cohort was 54 months. Survival was not significantly different between the 'del(5q)' group (median 55 months) and the 'del(5q) with ACA' group (median 38 months) (p=.75, Figure 1). This finding was consistent when analysis was restricted to patients in both groups treated with lenalidomide (p=0.29). The incidence of leukemic transformation in the del(5q) group was 5%, compared with 18% for the 'del(5q) with ACA' group (p=0.16), however there was no significant difference in LFS between the two groups (p=0.57). Conclusion : In our cohort of primary MDS patients meeting the 2016 WHO definition of 'MDS with isolated del(5q)', we confirm no significant survival difference between cases with del(5q) as the sole cytogenetic abnormality versus cases where del(5q) was accompanied by an additional cytogenetic abnormality. Table 1 Additional Cytogenetic Abnormalities with del(5q): Table 1. Additional Cytogenetic Abnormalities with del(5q): Figure 1 del(5q) vs del(5q) with an additional abnormality (ACA): Overall Survival Figure 1. del(5q) vs del(5q) with an additional abnormality (ACA): Overall Survival Disclosures Al-Kali: Onconova Therapeutics, Inc.: Research Funding; Celgene: Research Funding.

SummaryThe definition of the myelodysplastic syndrome (MDS) subtype ‘MDS with isolated del(5q)’ was expanded to include cases with one additional non‐chromosome 7 based cytogenetic abnormality in the 2016 revised World Health Organization classification. This study applied the revised definition to a large primary MDS cohort, and evaluated the prognostic impact of the additional cytogenetic abnormality. Seventy‐two of 1067 patients (7%) met the ‘MDS with isolated del(5q)’ criteria, 11 (1%) of whom had an additional cytogenetic abnormality. There was no survival difference between patients in whom del(5q) occurred alone, compared to those with one additional cytogenetic abnormality (P = 0·52).