LAUSR

Background: The RxPONDER trial demonstrated that chemotherapy improves survival in premenopausal, node-positive, HR+HER2- breast cancer patients irrelative of genomic risk. However, the rate of ovarian function suppression (OFS) was under 20%, questioning whether hormone therapy with OFS would be sufficient in genomic low risk patients. The survival outcome of premenopausal, node-positive, HR+HER2- breast cancer patients were retrospectively reviewed, to investigate the non-inferiority of only hormone therapy with OFS in this population. We also retrospectively reviewed patients who underwent genomic multigene assay in this population. Patients and methods: Breast cancer patients who underwent primary surgery between 1990 – 2013 at Asan Medical Center were retrospectively reviewed in this study. Patients who were 50 years old or younger, HR+HER2- breast cancer and T2/3N0 or T1/2N0 were included. Premenopausal patients who underwent the MAMMAPRINT® test between January 2018 – April 2021 were also reviewed and analyzed. Recurrence was defined as locoregional recur and distant metastasis. Disease-free survival (DFS) and distant metastasis-free survival (DMFS) was analyzed using the Kaplan-Meier survival analysis and log-rank test. Results: A total of 6,220 patients who were 50 years or younger underwent primary breast cancer surgery for HR+HER2- breast cancer between 1990 – 2013. Among them, 762 patients were T2/3N0 and 1,283 patients were T1/2N0. Most of the patients (N=1,652, 80.8%) underwent chemotherapy. Among patients who only had hormone therapy, 48 (12.2%) patients only had tamoxifen and 345 (87.8%) patients had tamoxifen with OFS (TAM+OFS). The median follow-up was 107 months. The 8-year DFS was 87.2% in the chemotherapy group, compared to 90.2% in the TAM+OFS group (log-rank test p-value 0.499). The 8-year DFMS had no significant difference also between the chemotherapy and TAM+OFS group also (90.7% vs. 93.5% retrospectively, log-rank test p-value 0.184). DFS and DMFS did not differ in the subgroup analysis of T2/3N0 and T1/2N0 too. A total of 270 premenopausal patients underwent the MAMMAPRINT® test for HR+HER2-, N1 breast cancer between Jan 2018 – April 2021. Among them, 136 (50.4%) patients had low genomic risk and 134 (49.6%) had high genomic risk. Among the low genomic risk patients, 17 (19.9%) patients had only tamoxifen, 107 (78.7%) had TAM+OFS and 1 (0.7%) patient had aromatase inhibitor. The median follow-up period was 26 months. There were seven recurrence events, 2 distant metastasis and 5 locoregional recurrences. Among the low genomic risk patients, 1 patient had lung metastasis and 1 patient had local recurrence. Both patients had only TAM+OFS. Conclusion: In this study, TAM+OFS showed no significant survival difference compared to chemotherapy in premenopausal, HR+HER2- patients. Patient selection is essential to omit chemotherapy in this population. The predictive value of genomic multigene assay for chemotherapy in premenopausal, HR+HER2-, node positive patients warrant further evaluation. Several clinical trials are being prepared to answer this question. Citation Format: Tae-Kyung Yoo, Sae Byul Lee, Youngwon Lee, Yunghyun Hwang, Eunju Shin, Jin Lee, Hee Jeong Kim, Il-Yong Chung, Beom Seok Ko, Jong Won Lee, Byung Ho Son. Chemotherapy is not mandatory in premenopausal, node-positive, HR+HER2- breast cancer patients [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 P2-03-21.