Abstract P3-05-02: Trends in clinical treatment of early stage ER+PR- breast cancer in the National Cancer Database

Abstract Background Estrogen receptor positive (ER+) progesterone receptor negative (PR-) tumors are a distinct subset of breast cancers that are not well characterized. It is critical to better understand the biology of ER+PR- tumors and tailor therapy accordingly for this unique subgroup. The objective of this study is to compare the ER+PR- subgroup of breast cancer as compared to the double positive ER+PR+ group in a large, well-characterized database to determine if the tumors that are PR- are associated with higher rates of genomic testing and chemotherapy receipt. Methods We identified patients diagnosed with ER+Her2-, Stage 1-3 invasive breast cancer from 2010-2015 in the National Cancer Database. We excluded patients who received neoadjuvant therapy. Demographics and clinical characteristics for the ER+PR+ and ER+PR- groups were obtained. Differences between groups were assessed using the chi-square test. Multivariable logistic regression analysis was performed on both the node negative and node positive patients in order to identify factors independently associated with having a genomic test and receiving chemotherapy in the ER+PR+ and ER+PR- cohorts. Results Of the 363,945 eligible patients, 327,357 (89.9%) patients had ER+PR+ breast cancer and 36,588 (10.1%) had ER+PR- breast cancer. A trend towards larger tumor size in the ER+PR- population as compared to the ER+PR+ population was noted with 23.1% vs 17.3% of tumors 2-5cm and 2.2% vs 1.2% of tumors > 5cm, respectively. Higher grade was also seen in the ER+PR- group as compared to the ER+PR+ group with 27.1% versus 11.7% grade 3 tumors. In both the node negative and node positive populations, genomic testing was less likely to be sent on a PR- breast cancer than a PR+ breast cancer. When genomic testing was sent, there were more high risk Oncotype Recurrence scores (RS > 30) in the PR- group than the PR+ group. For node negative breast cancer high risk Oncotype recurrence scores were found in 32.4% of the ER+PR- population versus 5.6% in the ER+PR+ population. In the node positive cohort high risk Oncotype Recurrence scores were seen in 27.8% of the ER+PR- population as compared to 5.0% in the ER+PR+ population. Patients with discordant ER+PR- breast cancer were more likely to receive chemotherapy than their ER+PR+ counterparts in both the node negative cohort (32.2% vs 12.7%) and the node positive cohort (73.2% vs 64.5%). Conclusion There have been limited studies to date specifically focused on the ER+PR- subgroup. Patients with ER+PR- breast cancer have a higher grade, larger size, higher risk genomic testing, and are more likely to receive chemotherapy than their ER+PR+ counterparts. Discordance in hormone receptor status contributes to a more aggressive type of breast cancer that may impact clinical and treatment decisions. Citation Format: Poornima Saha, Angeline Yu, Priya Thakkar, Kristine Kuchta, Katharine Yao. Trends in clinical treatment of early stage ER+PR- breast cancer in the National Cancer Database [abstract]. In: Proceedings of the 2022 San Antonio Breast Cancer Symposium; 2022 Dec 6-10; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2023;83(5 Suppl):Abstract nr P3-05-02.