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In myelodysplastic syndromes (MDS), cytogenetic characteristics of the malignant bone marrow cells influence the clinical course. The aim of this study was to evaluate whether cytogenetics is useful to predict outcome and response in patients with del(5q) under azacitidine (AZA) ± lenalidomide (LEN) therapy. We therefore performed comprehensive cytogenetic analyses in MDS patients with del(5q) treated within the randomized phase II trial NMDSG10B. Seventy-two patients were enrolled in the study and 46 patients (64%) had sufficient cytogenetics at inclusion and response evaluation. Karyotyping was significantly more sensitive during follow-up to detect del(5q) compared to FISH, 34 patients (97%) versus 27 patients (77%) (p = 0.027). The overall response rate (ORR) did not differ between the 11 patients with < 3 aberrations (median 1 aberration) and the 59 patients with ≥ 3 aberrations (median 7 aberrations, range 3–16), while ≥ 3 aberrations were associated with shorter overall survival (OS), 9.9 months versus 25.2 months (p = 0.004). OS was significantly shorter in patients with unbalanced translocation of 5q than patients with del (5)(q14q34), 8.4 months versus 21.1 months (p = 0.004). Both complex karyotype and multi-hit TP53 alterations were more frequent in patients with unbalanced translocations of 5q versus del (5)(q14q34), 98% and 88% versus 67% and 47% (each p = < 0.001). Most patients with cytogenetic progression had multi-hit TP53 alterations at inclusion. Cytogenetic progression occurred at a similar frequency in the AZA arm and in the AZA + LEN arm. In summary, this study in homogenously treated MDS patients with different abnormalities of 5q demonstrates the influence of cytogenetics on treatment results.

Trial Registration: EudraCT number: 2011-001639-21; ClinicalTrials.gov identifier: NCT01556477.