CST3 and breast cancer: PGS for serum cystatin C levels (T3) was associated with longer disease-free survival (HR = 0.82, 95% CI = 0.71–0.95), breast event-free survival (HR = 0.74, 95% CI = 0.61–0.91), and breast cancer–specific survival (HR = 0.72, 95% CI = 0.54–0.95).