Abstract P3-14-16: Prevalence of low estrogen receptor and low progesterone receptor positivity at an urban safety net hospital
Authors: Angell Callie , Bullock Jolonda , Diaz Anna , Basha Riyaz , Narra Kalyani 
Published: March 2022

Background: The American Society of Clinical Oncologists/College of American Pathologists guidelines were updated in January 2020 to account for a range of positivity in Estrogen Receptor expression (ER), with samples with 1-10% immunoreactive tumor cell nuclei being reported as ER low positive (low+). There is limited data on endocrine responsiveness of this group and ER low+ cancers tend to profile and behave more like typical triple negative breast cancers (TNBC). The significance of isolated Progesterone Receptor (PR) expression is still unclear even though it is reported between 1-100%. This project investigated the number of ER low+ breast cancer patients at John Peter Smith Hospital (JPS). JPS has a higher proportion of Black breast cancer patients than SEER. As Black patients are more likely to have TNBC than non-Hispanic white patients (NHW), JPS also has a higher proportion of TNBC. With ER low+ cancers behaving more like TNBC, this research was conducted to see if there were also more ER low+ patients at JPS. Methods: A retrospective study was conducted using data from the institutional registry of the JPS Oncology and Infusion Center in Fort Worth, TX. Eligible patients were diagnosed with invasive breast cancer in 2020. Data from the JPS Department of Pathology and analyzed for ER and PR expression percentage, Her2 status, race, and ethnicity. HR+ was defined as either ER or PR being 10-100%. JPS data was compared to SEER data from 2014-2018. Results: JPS had 119 eligible patients for this study; 36 NHW, 31 Black, and 47 Hispanic. Of these, 6 were ER low+ and 4 of those were Her2-. 2 of the ER low+ patients were Black and 4 Hispanic. There were 96 Her2- patients, with 26 ER-, 4 ER low+, and 66 ER+. Of the overall 35 ER- patients, 34 were also PR- and 1 was PR low+. 4 of the 6 ER low+ were PR- and 2 PR low+.

Conclusion: JPS has a higher percentage of ER low+ cases than previous studies conducted, with 2.6% and 1% found in literature review and 5% (95% CI: 1%, 9%) at JPS, but there is no national data to compare to yet. All the ER low+ patients at JPS were Black or Hispanic. This is limited by the number of ER low+ patients. Blacks and especially Hispanics were more likely to be ER- or ER low+ than NHW. They were also more likely to be PR-, with Black patients most likely to be PR low+. Black patients were most likely to be Her2-. For patients that were ER-, there was a strong concordance with PR status, with 1 case where PR was in a higher category and 86% of cases having ER and PR in agreement. Black and Hispanic patients account for 80% of TNBC at JPS. JPS has a significantly higher proportion of TNBC cases compared to SEER, with 21% (95% CI: 14%; 28%) of cases being TNBC and an additional 3.4% that are ER low+ and Her2-, therefore possibly behaving like TNBC. It is necessary to further investigate the significance of ER low+ and PR low+ expression, and for more research to be done on breast cancer in minority patients who are underrepresented in clinical trials but are more likely to have TNBC, which is aggressive and has poor survival rates.

Percentage of Each Status by RaceER-ER low+ER+PR-PR low+PR+Her2-Her2+TNBCNon-Hispanic White22.2%(8)0%(0)77.8%(28)30.6%(11)5.6%(2)63.9%(23)77.8%(28)22.2%(8)20%(5)Black29%(9)6.5%(2)64.5%(20)41.9%(13)16.1%(5)41.9%(13)87.1%(27)9.7%(3)24%(6)Hispanic31.9%(15)8.5%(4)59.6%(28)51.1%(24)6.4%(3)42.6%(20)80.9%(38)19.1%(9)48%(12)Other50%(3)0%(0)33.3%(2)66.7% (4)0%(0)16.7%(1)66.7%(4)16.7% (1)8%(2)Overall29.4%(35)5%(6)64.7%(77)42.9%(51)8.4%(10)47.9 %(57)80.7%(96)17.6%(21)(25)*One patient was Black Hispanic and was included in both rows as ER+ PR- Her2-

Comparison of Subtypes between JPS and SEERHR+ Her2-ER low+ PR- Her2-ER-PR low+ Her2 -HR-Her2- (TNBC)HR+ Her2+ER low+ PR- Her2+HR- Her2+UnknownJPS Cases by Subtype 202055.5% (66)3.4%(4)0.8%(1)21%(25)9.2%(11)1.7%(2)6.7%(8)1.7%(2)SEER Cases by Subtype 2014-201868%(included in HR+ Her2-)(included in HR+ Her2-)10%10%(included in HR+ Her2+)4%7%

Citation Format: Callie Angell, Jolonda Bullock, Anna Diaz, Riyaz Basha, Kalyani Narra. Prevalence of low estrogen receptor and low progesterone receptor positivity at an urban safety net hospital [abstract]. In: Proceedings of the 2021 San Antonio Breast Cancer Symposium; 2021 Dec 7-10; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2022;82(4 Suppl):Abstract nr P3-14-16.