Probability of 10-year overall survival according to molecular subtypes of SCD. Patients with hemoglobin S (HbS)/β⁰-thal who received hydroxyurea (HU) had a 87% probability of 10-year overall survival (OS) compared with 54% of non-HU patients (P = .001; A). The respective 10-year probability for HU patients with HbS/HbS and HbS/IVSI-110 was 100% (B), and 82% (C), whereas for non-HU patients these probabilities were 10% (P < .001; B) and 66% (p = 0.369; C), respectively.