High-dose estrogen as salvage hormonal therapy for highly refractory metastatic breast cancer: A retrospective chart review

Background: High-dose estrogens (HDEs) are an efficacious but widely overlooked treatment option for patients with metastatic breast cancer (MBC). This is due in part to the introduction of tamoxifen in the 1970s, which was proven to be equivalent in efficacy and associated with fewer adverse events (AEs). Objective: The aim of this study was to report our experience with the use of HDE in postmenopausal women with advanced breast cancer. Methods: Local institutional review board approval was obtained to conduct a retrospective chart review of patients with MBC treated with HDEs at the Boca Raton Comprehensive Cancer Center, Boca Raton, Florida, from 2001 through March 2009. Demographic information, response rates, and tolerability profiles were collected. Results: Of the 426 patients with MBC identified, we found 26 patients with MBC who were prescribed HDEs as a treatment in any line of therapy for advanced breast cancer. The median age at the start of HDE therapy was 59 years (range, 42-92 years). Three of the 26 patients (11.5%) were human epidermal growth factor receptor 2-positive determined via fluorescent in situ hybridization analysis. With the exception of 1 patient who had received no prior systemic treatment for metastatic disease, all patients received multiple lines of treatment (both chemotherapy and hormonal treatments) in the advanced setting (median, 7 lines; range, 0-12) prior to the initiation of HDE. Five of 20 patients (25%) with measurable metastatic disease (visceral and/or soft tissue metastases) had objective antitumor responses defined as either a partial response (PR) or a complete response (CR). Four additional patients (20%) had prolonged stable disease (SD) for ≥6 months. Three of 6 patients (50%) with nonmeasurable metastatic disease (bone-only) had prolonged SD for ≥6 months. Clinical benefit rate (defined as CR + PR + SD ≥6 months) for all patients was 46% (12/26), with a median duration of 10 months. Overall median progression-free survival for the 26 subjects was 5 months. Median survival from the start of HDE was 17 months (range, 3-54 months). AEs included fluid retention (8 [31%]), vaginal bleeding (7 [27%]), and nausea (4 [15%]). Two patients discontinued therapy after 1 month. Three of the remaining 24 patients discontinued estrogen therapy due to AEs. Conclusions: This retrospective chart review details our facility's experience with the use of HDE in patients with advanced breast cancer, most of whom had received multiple prior treatments. Our data suggest that this treatment is another option for heavilytreated patients in whom further endocrine manipulation might still be appropriate.