Negative progesterone receptor status is an adverse prognostic factor for luminal B breast cancer

Progesterone receptor (PR) is involved in tumor but its prognostic value in breast cancer remains unclear. This study aimed to investigate whether PR status is a prognostic factor for luminal B breast cancer. Total 209 patients with invasive breast cancer were enrolled. We found that PR-negative luminal B breast cancer was significantly associated with older age. PR-negative subgroup showed significantly worse median disease-free survival (mDFS) than PR-positive subgroup with a hazard ratio (HR) of 1.80 (95% confidence interval [CI] 1.05-3.09). PR-negative subgroup also had an increased risk for non-visceral metastases (HR= 2.17, 95% CI 1.09-4.31) as well as a trend toward higher risk for locoregional relapse (HR= 2.23, 95% CI 0.95-5.26), compared to PR-positive subgroup. Furthermore, in HER2-negative patients, the HRs for mDFS, non-visceral metastases, and locoregional relapse were 2.54 (95% CI: 1.21-5.33), 2.79 (95% CI: 1.07-7.22), and 4.23 (95% CI: 1.34-13.40), respectively. Multivariate analysis showed that PR-negative status, lymph node positive cancer, and not receiving adjuvant radiotherapy were associated with reduced DFS and increased risk for non-visceral metastases and locoregional relapse. For patients with radiotherapy, PR-negative status remained a significant predictor of all outcomes, with HRs of 1.89 (95% CI: 1.11-3.21), 2.67 (95% CI: 1.36-5.24), and 2.47 (95% CI: 1.05-5.81) for DFS, non-visceral metastases, and locoregional relapse, respectively. In conclusion, PR-negative status is an independent adverse prognostic factor for luminal B breast cancer.