Impact of somatic mutations in myelodysplastic patients with isolated partial or total loss of chromosome 7

Monosomy 7 [−7] and/or partial loss of chromosome 7 [del(7q)] are associated with poor and intermediate prognosis, respectively, in myelodysplastic syndromes (MDS), but somatic mutations may also play a key complementary role. We analyzed the impact on the outcomes of deep targeted mutational screening in 280 MDS patients with −7/del(7q) as isolated cytogenetic abnormality (86 with del(7q) and 194 with −7). Patients with del(7q) or −7 had similar demographic and disease-related characteristics. Somatic mutations were detected in 79% (93/117) of patients (82% in −7 and 73% in del(7q) group). Median number of mutations per patient was 2 (range 0–8). There was no difference in mutation frequency between the two groups. Patients harbouring ≥2 mutations had a worse outcome than patients with <2 or no mutations (leukaemic transformation at 24 months, 38% and 20%, respectively, p = 0.044). Untreated patients with del(7q) had better overall survival (OS) compared with −7 (median OS, 34 vs 17 months, p = 0.034). In multivariable analysis, blast count, TP53 mutations and number of mutations were independent predictors of OS, whereas the cytogenetic subgroups did not retain prognostic relevance. This study highlights the importance of mutational analysis in terms of prognosis in MDS patients with isolated −7 or del(7q).