P1-09-09 Disparities in second breast cancer events and survival persist despite optimal treatment in hormone-receptor positive breast cancer: Analysis of the real-world ASCO CancerLinQ dataset

ASCO CancerLINQ was used to identify pts that underwent surgery for invasive HR+HER2- stage I-III BC from 2005-2022. We defined SBCE as a second event in the ipsilateral or contralateral breast or axilla after prior treatment for BC. Optimal treatment was defined to include adjuvant endocrine therapy, radiation after lumpectomy in age <70, and regional nodal irradiation for N2-N3 disease. Patient characteristics and rates of SBCE were examined by self-reported race and ethnicity. Kaplan-Meier analysis was used to estimate SBCE-free survival and OS in optimally and not-optimally treated pts.

Among 40,917 HR+HER2- BC pts, 27,803 (68.0%) were Non-Hispanic White (NHW), 4,193 (10.3%) Non-Hispanic Black (NHB), 1,767 (4.3%) Hispanic, 1,112 (2.7%) Asian or Pacific Islander (API), and 6,042 (14.8%) other or unknown race and ethnicity. NHW pts were more likely to present with clinical stage I disease (60.8% vs 50.5%, 50.1%, and 55.4% for NHB, Hispanic, and API pts respectively, p<0.01), and be older at diagnosis (16.6% of NHW vs 21.5%, 33.0%, and 31.9% of NHB, Hispanic, and API pts were age <50, p<0.01). Overall, 66.7% of NHW, 70.3% of NHB, 73.3% of Hispanic, and 76.0% of API pts received optimal treatment for all eligible definitions (p<0.01). 5-yr estimated SBCE-free survival in optimally treated pts was 98.4%, 98.3%, 98.8%, and 98.0% for NHW, NHB, Hispanic, and API patients (p<0.01). In pts without optimal treatment, this decreased by 0.5%, 0.1%, 0.9%, and 1.0%, respectively. 5-year OS in optimally treated pts was 94.5%, 93.4%, 97.2%, and 97.2% in NHW, NHB, Hispanic, and API patients (p<0.01). In pts without optimal treatment, this decreased by 3.1%, 4.1%, 2.1%, and 0.1%, respectively.

Differences in SBCE and OS were seen by race and ethnicity in HR+HER2- BC, including in pts receiving optimal treatment. This adds granular real-word evidence to support racial and ethnic disparities are pronounced in HR+HER2- BC despite similar treatment.