PARP1 and breast cancer: A meta-analysis included 3506 patients from eight studies, the results indicated that higher PARP expression indicated a worse clinical outcome in early stage breast cancer, with a HR of 3.08 (95% CI, 1.14 ± 8.29, P = 0.03) for disease-free survival and a HR of 1.82 (95% CI, 1.20 ± 2.76; P = 0.005) for overall survival23.