Abstract P3-08-05: Impact of estrogen receptor levels on outcome in triple negative breast cancer patients treated with (neo)adjuvant chemotherapy

Abstract

Abstract Background: Although 1% is recommended by guidelines as cut-off for estrogen receptor (ER) positivity, the 10% cut-off is often used in clinical practice based on studies showing that breast cancers with ER ≥1% &<10% have biological characteristics and prognosis similar to those with ER <1%. Our aim was to compare disease-free survival (DFS) and overall survival (OS) according to ER level in a cohort of patients with HER2-negative, ER<10% and progesterone receptor <10% undergoing (neo)adjuvant chemotherapy. Methods: Clinicopathological data of patients with triple negative breast cancer (defined as ER and progesterone receptor <10% and HER2-negative) treated at our Institution with (neo)adjuvant chemotherapy between January 2000 and April 2019 were collected. Patients were categorized according to ER expression; <1% or ≥1%&<10%. Pathologic complete response (pCR) was defined as ypT0/is and ypN0. DFS was calculated from date of diagnosis to date of relapse (locoregional or distant), death or last follow up. OS was calculated from the date of diagnosis to date of death or last follow up. Hazard ratios and 95% CI were calculated with the Cox proportional hazard regression model. Results: 406 patients were included: 364 with ER<1%, 42 with ER≥1%&<10%. Main characteristics: median age 54 years (range 25-84), ductal histology 91% (N 367), grade 3 88% (N 350), median ki67 58%, stage at diagnosis: I 33% (N 134), II 52% (N 212), III 15% (N 59). There was no significant difference in clinicopathological characteristics according to ER level. However, ER≥1%&<10% tumors had a numerically higher frequency of advanced disease stages (I 19% N=8, II 57% N=24, III 24% N=10, p=0.057).Almost half of the patients (41%, N=165) received neoadjuvant chemotherapy: 39% in the ER<1% and 57% in the ER≥1%&<10% cohort (p=0.032). pCR was achieved by 63 patients (38%). pCR rate was similar in the two cohorts (38% in ER<1% cohort, 44% in ER≥1%&<10% cohort, p=0.498). 274 patients (67%) received adjuvant chemotherapy (41 after previous neoadjuvant treatment): 69% in the ER<1% and 55% in the ER≥1%&<10% cohort (p=0.092). With a median follow up of 54 months, 88 patients had relapsed and 64 died. No difference in DFS and OS was observed according to ER levels: 5-year DFS was 73.7% in ER<1% and 73.1% in ER≥1%&<10% cohort (log-rank p=0.610); 5-year OS was 82.3% in ER<1% and 76.7% in ER≥1%&<10% cohort (log-rank p=0.820). Disease stage at diagnosis was the only clinicopathological variable significantly associated with DFS and OS in the overall study cohort (data not shown). DFS and OS Hazard Ratios for ER≥1%&<10% tumors as compared to ER<1% tumors at univariable analysis and after correction by stage are presented in the table. Conclusions: Early HER2-negative primary breast cancer with ER <10% behaves clinically like ER<1% breast cancer in terms of DFS and OS after (neo)adjuvant chemotherapy. Our results support the definition of TNBC as HER2-negative breast cancer with ER<10% and PgR<10%, rather than <1%. DFS and OS Hazard Ratios for ER≥1%&<10% tumors as compared to ER<1% tumorsDFSHazard Ratio (95% CI)Hazard Ratio (95% CI) corrected by stagep-valueER<1%RefRef0.957ER≥1%&<10%1.19 (0.61-2.30)0.98 (0.51-1.91)OSHazard Ratio (95% CI)Hazard Ratio (95% CI) corrected by stagep-valueER<1%RefRef0.805ER≥1%&<10%1.10 (0.50-2.40)0.90 (0.41-2.00) Citation Format: Gaia Griguolo, Maria Vittoria Dieci, Michele Bottosso, Vassilena Tsvetkova, Carlo Alberto Giorgi, Silvia Angelini, Giulia Tasca, Enrico Cumerlato, Marcello Lo Mele, PierFranco Conte, Valentina Guarneri. Impact of estrogen receptor levels on outcome in triple negative breast cancer patients treated with (neo)adjuvant chemotherapy [abstract]. In: Proceedings of the 2019 San Antonio Breast Cancer Symposium; 2019 Dec 10-14; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2020;80(4 Suppl):Abstract nr P3-08-05.