Amongst Women Stratified to Receive Endocrine Therapy on the Basis of Their Tumor Estrogen and Progesterone Receptor Levels, Those with Higher Tumor Progesterone Receptor Levels Had a Better Outcome Than Those with Lower Levels of Tumor Progesterone Receptor

Background: To realize the association between stratified expression levels of ER and PgR and long-term prognosis of breast cancer patients who received adjuvant hormone therapy, this study aimed to propose better prognostic cut-off levels for estrogen receptor (ER) and progesterone receptor (PgR). Methods: Patients who received adjuvant hormone therapy after surgical intervention were selected. The ER and PgR status and their effects on breast cancer-specific survival (BCSS) and disease-free survival (DFS) over 5 and 10 years were evaluated. Next, subgroups were generated based on ER and PgR expression percentage and Allred scores. Survival curves were constructed using the Kaplan–Meier method. Results: ER and PgR expression were significantly associated with better prognosis in 5 years, whereas only PgR expression was significantly associated during the 10-year follow-up. The optimal cut-off values for better 5-year BCSS were ER > 50%; ER Allred score > 7; PgR ≥ 1%; or PgR Allred score ≥ 3; the corresponding values for DFS were ER > 40%; ER Allred score > 6; PgR > 10%; or PgR Allred score ≥ 3. In the long-term follow-up, PgR of > 50% or Allred score of > 5 carriers revealed a better prognosis of both BCSS and DFS. Conclusion: Patients with a PgR expression > 50% or an Allred score > 5 exhibited better 10-year BCSS and DFS.

Translational relevance of androgen receptor immunohistochemistry scoring systems for data harmonization in triple negative breast cancer (TNBC).

1078 Background: Androgen receptor (AR) expressing triple negative breast cancer (TNBC) is a sub-set of TNBC with an evolving prognostic and predictive behaviour. AR immunohistochemical threshold for positivity has not been standardized and a wide range of cut-offs have been used across studies ( > 0% to 75%). In this study we explored AR immunohistochemistry thresholds in relation to disease free survival (DFS) and clinical outcomes in non-metastatic TNBC using the Allred and H-Score systems. Increasing interest in AR as a therapeutic target for TNBC and the use of digital tissue image analysis makes it important to standardize AR immunohistochemistry reporting. Methods: 100 FFPE (formalin-fixed paraffin-embedded) tumour blocks were retrieved for non-metastatic TNBCs diagnosed between January 2015 and May 2017 and immunostained using AR441 (IgG1) mouse monoclonal antibody. Clinical follow-up ranged from 59 to 31 months and DFS was calculated. Cut-off scores were explored using Evaluate Cutpoints ( R maxstat package) and X-tile software. The score with maximum split in DFS (based on log-rank statistics and lowest p-value) was chosen as the cut-off. Descriptive and survival statistics was performed. Results: The median age was 51 (SD 11.262; range 28 to 82) years. Using Evaluate Cutpoints ≥3 was found as the threshold for AR by Allred Score. 36% cases were AR positive using Allred score (HR 0.508; CI 0.234 - 1.11; p-value 0.08). Using Evaluate Cutpoints ≥30 was found as the threshold for AR by H-Score (HR 0.624, CI 0.306 - 1.27; p-value 0.19). 35% cases were AR positive using H-Score. X-tile analysis also found the cut-offs as ≥3 and ≥30 for Allred and H-Score respectively (p < 0.05). A significant correlation was seen between the two scoring systems (Pearson Correlation 0.935; p < 0.01). A significantly higher number of grade III TNBCs were AR negative (n = 55/76) compared to grade II (n = 9/24) (p = 0.002). Cut-off for Ki67 was 75 (HR 1.61, CI 0.85-3.04, p-value 0.141) with a significantly higher number of AR negatives in the Ki67≥75 group (21/26; p < 0.05). The overall median DFS was 51.9 months. There was no significant difference in DFS for the AR negative (median: 47.4 months; mean: 39.39 months) and AR positive (Median survival not reached; mean: 41.3 months) groups(p = 0.23). Conclusions: AR immunohistochemistry cut-offs using the Allred (≥3) and H-Score (≥30) are close to the ones used for ER/PR immunohistochemistry as per ASCO/CAP guidelines, making a strong case for universal application of these systems for harmonization of AR data.

Effect of estrogen and progesterone receptor expression on progression-free and overall survival outcomes in low-grade serous ovarian cancer.

5560 Background: Research on ER/PR receptor function in low-grade serous ovarian cancer (LGSC) and the determinants of response to treatment are lacking. A recent study (Sehouli et al.,2018) described ER/PR immunohistochemistry (IHC) cut-points that distinguished PFS. Thus, we report on a group of patients with ER/PR expression by IHC in tumor samples of patients with LGSC and used this information to evaluate survival outcomes. Methods: Clinical information and FFPE sections were obtained from the Canadian Ovarian Experimental Unified Resource (COEUR). Tissue microarray (TMA) sections were stained for ER/PR using standard IHC techniques (MK). 50 stage 3 and 5 stage 4 patients were analyzed. ER/PR expression was scored using a simple scoring system ( < 1% cells staining, 1-50%, and ≥ 50%) and Allred scoring. We compared Kaplan-Meier (KM) survival (PFS and OS) curves using Log rank testing and Cox regression was used to model predictive/prognostic factors. A p-value of 0.05 was considered significant. Results: The mean age of the population was 49.5 years (SD;13.7). Ninety percent of patients were treated by surgery followed by platinum-based chemotherapy (PBC). Simple scoring did not discriminate outcomes as well for ER levels. PR Allred score ( < 2, vs 2- < 6 vs ≥6) clearly discriminated KM curves for PFS (p = 0.036) and OS (p = 0.01). For Allred ER score ( < 7 vs.7- < 8 vs 8) did not distinguish PFS (p = 0.4) but notably most patients received PBC after surgery. ER Allred score significantly distinguished OS (p = 0.008). Significant factors on Cox regression for PFS were residuum (p = 0.008;95%CI:1.2-3.1) and PR (p = 0.05;95%CI:0.39-0.99), whereas for OS ER(p = 0.01:95%CI:0.2-0.8) and residuum (p = 0.04;95%CI:1-2.8). Conclusions: ER/PR expression by Allred scoring was associated with PFS and OS. Patients will benefit from much needed research on ER/PR prediction/prognosis in LGSC. This work can inform clinical trials selection/stratification and patient selection for endocrine treatment.

ANZ1001 SORBET: Study of estrogen receptor beta and efficacy of tamoxifen, a single arm, phase II study of the efficacy of tamoxifen in triple-negative but estrogen receptor beta-positive metastatic breast cancer.

TPS1136 Background: Targeted therapies are needed for triple negative breast cancer (BC). ERβ is expressed in at least 20% of triple negative BCs. ERβ binds estrogen and tamoxifen with a similar affinity to ERα. ERβ has 5 isoforms but only ERβ1 is fully functional. ERβ expression has been shown to be significantly associated with improved distant disease free survival and better overall survival in tamoxifen treated ERα negative patients in retrospective studies. This “proof of principle” study will determine the efficacy of tamoxifen in patients with triple negative but ERβ positive metastatic BC. Methods: This single arm phase II study, being conducted by the Australia and New Zealand Breast Cancer Trials Group, has a Simon's 2 stage optimal design. The primary end-point is objective response rate (complete and partial responses). Progression free survival and clinical benefit rate will also be assessed. Eligibility criteria include histologically or cytologically confirmed metastatic triple negative BC (ER and PR absent, HER2 ISH negative or IHC 0 or 1) and measureable disease as per RECIST 1.1. Consenting patients undergo central ERβ testing and confirmation of triple negative status on a metastatic biopsy sample. ERβ positive patients (ERβ1 nuclear staining with Allred score >4) are offered trial participation. To date 12 potentially eligible patients have been screened for ERβ; 4 had Allred score >4 (although 2 of these subsequently proved to be ineligible for the trial), 7 had Allred scores <4 and 1 result is pending. Consenting patients receive tamoxifen 20mg per oral daily until disease progression, unacceptable toxicity or withdrawal of consent. If there are ≥2 responses in the first stage of 28 patients, an additional 38 patients will be accrued. Tamoxifen will be considered worthy of further research if there are ≥6 responses in the total 66 patients recruited. Current accrual is 1. Registered on ANZCTR (12610000506099).

ESR1 gene amplification and protein expression in 946 patients with resected breast cancer: A Hellenic Cooperative Oncology Group (HeCOG) translational research study.

592 Background: Discrepant data have been reported on the incidence of ESR1 gene amplification in breast cancer, its correlation to clinicopathologic characteristics and its impact on prognosis. Methods: Formalin-fixed paraffin-embedded (FFPE) tumor tissue samples from 946 patients participating in two adjuvant chemotherapy phase III trials (HE10/97 and HE10/00) were centrally assessed in tissue microarrays by immunohistochemistry (IHC) for estrogen receptor (ER), progesterone receptor (PgR) and human epidermal growth factor receptor 2 (HER2). FISH was also performed for HER2, TOP2A and ESR1 using commercially available dual (for ESR1) and triple (for HER2 and TOP2A) hybridization probes. Results: The majority of patients had >T2 (69%), node-positive, ER-positive (>1% stained cells, 73%) tumors managed with resection, chemotherapy and hormonotherapy (76%). Only 38 tumors (4.0%) had ESR1 gene amplification (ESR1/CEN6 ratio >2) and 514 (54.3%) ESR1 gene gain (1<ratio<2). The number of ESR1 gene copies was 3-4 in 251 (26.5%) and 5-10 in 42 (4.4%) of cases. HER2 and TOP2A gene amplification was seen in 234 (25.3%) and 101 (10.9%) of tumors, respectively. We studied the immunohistochemical expression of ER protein by evaluating the percentage of stained cells, the Allred score (0-2, 26.8%; 3-6, 62.5%; 7-8, 10.7% of tumors) and the semiquantitative H-Score (50-100, 13.8%; 101-200, 36.8%; 201-300, 15% of tumors). ESR1 gene amplification was significantly associated with taxane therapy, age >50, postmenopausal status, grade III-IV, absence of HER2 amplification and ER protein expression (p<0.05). At a median follow-up of 92 months, univariate Cox regression analysis showed that ER protein expression, but not ESR1 gene status, was a predictor of favorable outcome. In multivariate analysis, tumor size >5 cm, >4 involved nodes and negative/low ER protein expression by Allred score were independent adverse prognostic factors. Conclusions: Our data showed a rather low incidence of ESR1 gene amplification and failed to confirm its prognostic/predictive utility. ESR1 mRNA expression data will be presented at the meeting.