PIK3CA and breast cancer: The pooled SE and SP of PIK3CA mutation detection in cfDNA of breast cancer was 0.86 (95% confidence interval [CI] 0.32–0.99) and 0.98 (95% CI 0.86–1.00), respectively; the pooled PLR, NLR were 42.8 (95% CI 5.1–356.9) and 0.14 (95% CI 0.02–1.34), respectively.