STAT5A and breast cancer: Likewise, in Material IV, AQUA-quantified Nuc-Stat5a was an independent prognostic indicator of breast cancer-specific survival, as reflected in a 2.2-fold increased risk of death (CSS; multivariate Weibull regression HR = 2.15 (1.02, 4.55), P = 0.045; n = 190; Table 2).