In multivariate analysis of OS, older age (>70 years, HR = 4.85, 95% CI 2.347–15.471, p < 0.001), prior thrombosis history (HR = 5.66, 95% CI 2.784–29.456, p = 0.002), and resistance to HU according to mELN (HR = 4.11, 95% CI 2.933–20.477, p < 0.001) or ELN (HR = 3.98, 95% CI 2.743–16.941, p = 0.001) criteria were independent prognostic factors (Table 4). This evidence concerns the gene ELN and deep vein thrombosis.