Abstract P3-07-10: The association between the expression of progesterone receptor and clinical benefit of adjuvant trastuzumab in estrogen receptor-positive and HER2-positive breast cancer patients

Abstract

Abstract Background: Previous studies have shown that progesterone receptor (PR) status has a prognostic value in hormone receptor-positive breast cancer. In this study, we evaluated the clinical significance of PR status in estrogen receptor (ER)-positive and HER2-positive breast cancer. Methods: We retrospectively analyzed the data of ER+ and HER2+ breast cancer patients who underwent surgery at Gangnam Severance hospital and Severance hospital from 2002 to 2012. We excluded patients who had a history of previous cancer, received neoadjuvant chemotherapy, did not received adjuvant chemotherapy, and had contralateral breast cancer or metastasis at diagnosis. A total of 346 patients were identified. Among them, 155 patients (44.8%) received adjuvant trastuzumab. Results: At a median follow-up of 59 months, median disease-free survival (DFS) and overall survival (OS) were 56 and 59 months, respectively. The DFS and OS showed no difference according to PR status in overall patients. Then, these patients were categorized into two groups: ER+/HER2+/PR+ and ER+/HER2+/PR-. In ER+/HER2+PR+ patient, there was no difference of DFS or OS according to trastuzumab use. In ER+/HER2+/PR- patients, DFS was significantly better in patients who received adjuvant trastuzumab treatment compared to those who did not (p=0.009). We also analyzed influence of PR status on treatment outcome between patients who received adjuvant trastuzumab and those who did not. In patients who received adjuvant trastuzumab, there was no difference of DFS or OS according to PR status. However, in patients who did not receive adjuvant trastuzumab, ER+/HER2+/PR- patients showed worse DFS than ER+/HER2+/PR+ patients (p=0.006). Conclusions: In patients with ER+/HER2+ breast cancer, we found that a prognostic value of PR only retained in those who did not receive adjuvant trastuzumab. Our findings suggest that the use of adjuvant trastuzumab may offer less clinical benefit for the patients with ER+/HER2+/PR+ breast cancer. Citation Format: Lee HW, Ahn SG, Park JT, Yang BS, Park S, Jeong J, Kim SI. The association between the expression of progesterone receptor and clinical benefit of adjuvant trastuzumab in estrogen receptor-positive and HER2-positive breast cancer patients. [abstract]. In: Proceedings of the Thirty-Eighth Annual CTRC-AACR San Antonio Breast Cancer Symposium: 2015 Dec 8-12; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2016;76(4 Suppl):Abstract nr P3-07-10.