Higher expression of estrogen receptor in primary platinum-resistant high grade serous ovarian cancers

Introduction: Endocrine therapy for ovarian cancer is an option and commonly used in pretreated patients. Unfortunately, the benefit of this therapy is small with low response rates. Prognosis and treatment benefit depends on estrogen (ER) and progesterone receptor (PR) expression. The aim of this study is to determine the expression rate of ER and PR in a high-risk serous ovarian cancer cohort.

Methods: Matched primary and recurrent high-grade serous ovarian cancers collected between 1985 and 2003 at the University Hospital Basel within a Tissue Microarray were used for this study (n = 80). All patients had complete debulking surgery and adjuvant platinum-based chemotherapy. Immunohistochemistry for ER/PR expression was analyzed by two independent pathologists. The scoring system included percentage and intensity of staining.

Results: All patients had at least 3 cycles of platinum-based chemotherapy, with 73 patients (91.3%) receiving a full six-cycle course. ER expression was higher in chemotherapy-resistant primary tumors (33.3%) than in their recurrent counterparts (19.0%), and was also higher in chemotherapy-resistant compared to chemotherapy-sensitive primary tumors (33.3 vs. 23.1%). PR expression was significantly higher in primary (27.5%) than in recurrent counterparts (13.9%) (p = 0.046), and was higher in chemotherapy-sensitive primary (29.2%) than in their chemotherapy-sensitive recurrent counterparts (13.5%).

Conclusion: In this small unique collection there was an increased ER and significantly increased PR expression in primary compared to relapsed ovarian cancers and a higher expression of ER in chemotherapy-resistant cancers. ER targeted therapy therefore may be an option in ER positive chemotherapy-resistant disease.