Prognostic Value of Progesterone Receptor and Ki-67 Combination in Hormone Receptor Positive Grade 2 Early-stage Breast Cancer

  Objective  To evaluate the prognostic value of the combination of progesterone receptor (PR) and Ki-67 index in grade 2 breast cancer with positive hormone receptor (HR) and negative axillary lymph node.

  Methods  The clinical and pathological data of patients with grade 2 breast cancer who underwent surgical treatment and 21 genes' recurrence score (RS) testing in the department of Breast Surgery, Peking Union Medical College Hospital from May 2012 to May 2017 were retrospectively analyzed. According to the 21 genes' RS, patients were divided into RS low-risk group (RS < 18), RS intermediate-risk group (18≤RS < 31), and RS high-risk group (RS≥31). At the same time, the combination of PR and Ki-67 index (PK) was set according to the expression of PR and Ki-67 index. The patients were divided into PK low-risk group (PR≥10% and Ki-67≤20%), PK high-risk group (PR < 10% and Ki-67>20%), and PK intermediate-risk group (non-high or low-risk group). The consistency of the PK combination and 21 genes' RS was analyzed and compared.

  Results  A total of 389 patients who met the inclusive and exclusive criteria were enrolled in this study, including 247 patients in RS low-risk group (63.5%, 247/389), 115 in RS intermediate risk group (29.6%, 115/389), 27 in RS high-risk group (6.9%, 27/389), 248 in PK low-risk group (63.8%, 248/389), 125 in PK intermediate risk group (32.1%, 125/389), 16 in PK high-risk group (4.1%, 16/389). The predictive sensitivity of the recommended PK combination for RS low risk and high-risk group was 75.3% and 37.0%, respectively, with the positive predictive values of 75.0% and 62.5%, and the inconsistency of 0.4% and 6.3%, respectively. After a median follow-up of 40 months, the total incidence of locoregional recurrence (LRR) and distant metastasis (DM) in PK low, intermediate, and high-risk group was 3.6%, 7.2%, and 12.5%, respectively. The total incidence of LRR and DM in RS low, intermediate, and high-risk groups was 3.2%, 8.7%, and 7.4%, respectively. There was no significant difference between PK combination and RS (P=0.655).

  Conclusion  The prognostic value of PK combination for HR-positive grade 2 early-stage breast cancer with negative axillary lymph nodes is comparable to that of the 21 genes' RS.