PIK3CA and breast cancer: Subsequently we conducted subgroup analysis in 152 ER positive breast cancers and found that there was a statistically significant difference in 5-year DFS between ER positive PIK3CA mutant and PIK3CA wild-type patients (54.2% vs. 76.2%; P = 0.011; HR = 2.383; 95%CI, 1.199–4.738; Fig. 2D).