Abstract P1-08-18: Impact of gene expression profile testing for lymph node positive (LN+) , hormone receptor positive (HR+), HER2 negative (HER2-) breast cancer (BC) patients on the use of adjuvant chemotherapy in a large community cancer center

Abstract Background: Use of gene expression profiling (GEP) is considered standard of care, in deciding use of adjuvant chemotherapy in patients with LN negative breast cancer. However, there are limited data for the use of GEP in LN+ disease. Both Mammaprint™ and Oncotype Dx 21 gene recurrence score™ (RS) have been evaluated in LN+ disease, the data are not as robust as in the LN- population. Based on data from the RXPONDER trial and the MINDACT trial, the NCCN has recently recommended the use of Oncotype Dx to help decide the utility and benefit of adjuvant chemotherapy after resection in LN- , Hormone receptor Positive (HR+), HER2 negative (HER2-) breast cancer patients. Because of the potential major impact of these data on patient management and healthcare utilization, we decided to explore the uptake and implementation of this testing at a large community cancer center in order to assess and report real world data pertaining to this novel standard of care. Methods: Database search of the Electronic Medical Records used at Ironwood Cancer Center, revealed 2455 newly diagnosed patients with early stage breast cancer during the period from 1/1/2018 till 6/1/2021. HIPAA deidentified data was extracted with inclusion criteria of newly diagnosed women with LN+ (1-3 nodes), HR+, and Her2- which yielded 403 patients. Demographics & treatment data: Characteristics included menopausal status (Premenopausal 23%, Post Menopausal 77%), Surgery type (mastectomy 44%, breast conservation surgery 56%), size of primary tumor (0-1 cm 16 %, 1-2 cm 28%, 2-5 cm 43%, and > 5 cm 13%), LNs resected (Range 0-37, Median 4), # of LNs +(1-60%, 2-25%, 3-15%), and Tumor Grade (Grade 1-23%, 2-56%, 3-21%). GEP was performed in 62% of the patients. 49% received adjuvant chemotherapy (61% anthracycline based, 39% non anthracycline based). Of the patients tested, 41% received adjuvant chemotherapy. Adjuvant antihormonal therapy included aromatase inhibitors in 86% and Tamoxifen in 14%. 81% of the pre-menopausal patients received complete ovarian suppression. Results: Logistical Regression analysis in a non linear fashion, R2 data and Chi-square analysis was used to test the statistical significance of the observed relationship with respect to the expected relationship. The data was divided into 6 monthly intervals to allow comparison of the uptake of the test and impact on adjuvant chemotherapy decision making. There was a significant increase in GEP profile testing percentages when these intervals were compared across the years (R2 =0.69). Increase in GEP profiling was associated with lower utilization of adjuvant chemotherapy (R2= 0.84). There was a non-significant decline in the use of adjuvant chemotherapy (Chi2 NS, p value 0.22). Menopausal status, grade/size of tumor did not meet the statistical significance for the likelihood of utilization of the test. Currently multivariate analysis is being performed to examine the interplay between the numerous clinical factors on which the data was collected. This analysis will allow us to decide if we can longitudinally explore recurrence rates in each of these subsets. Conclusion: GEP has seen a significant uptake to help with adjuvant chemotherapy decision making in LN + (1-3) patients in the community cancer center setting over the last 4 years. These real world data also showed that increased testing was associated with decreased chemotherapy use which has translated to lowering health care resources and minimizing patient morbidity. Recommendations from the expert guidelines and clinical trial data have helped accelerate the use of this technology in the decision making to undergo adjuvant chemotherapy in the LN+, HR+, HER2- patients with breast cancer. Citation Format: Nisha Rao Kalmadi, Andrew Brown, Manas Sharma, Mikhail Shtivelband, Joshua Rifkind, Sujith Kalmadi, Rajesh Bagai, Emily Ho, Patricia Clark, Christopher Kellogg, Parvinderjit Khanuja. Impact of gene expression profile testing for lymph node positive (LN+) , hormone receptor positive (HR+), HER2 negative (HER2-) breast cancer (BC) patients on the use of adjuvant chemotherapy in a large community cancer center [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 P1-08-18.