Fig. 3

Kaplan–Meier estimates of probability of overall survival in patients with metastatic breast cancer. Comparison between patients with higher/lower A circulating tumour cells (p < 0.0001, chi-square = 26.372, hazard ratio = 2.870, 95% CI for HR = 1.876–4.392), B circulating free DNA (p < 0.0001, chi-square = 14.701; hazard ratio = 2.296, 95% CI for HR = 1.476–3.570), C CA15-3 (p < 0.0001, chi-square = 18.006; hazard ratio = 2.876, 95% CI for HR = 1.717–4.816) and D AP (p < 0.0001, chi-square = 28.710; hazard ratio = 3.063, 95% CI for HR = 1.982–4.732). p value obtained by the log-rank test. Hazard ratio and 95% CI obtained by Cox proportional-hazards regression analysis