GSTM1 and anemia (phenotype): In multivariate analysis of TFS, older age (>70 years, HR = 6.81, 95% CI 2.668–17.528, p < 0.001), presence of anemia (Hb <12 g/dL, HR = 5.55, 95% CI 1.745–17.655, p < 0.001), and resistance to HU according to the mELN criteria (HR = 3.825, 95% CI 1.687–8.851, p = 0.001) were independent prognostic factors (Table 4).