Abstract P2-03-06: Real world treatment of node negative low and intermediate recurrence score breast cancer
Authors: Globus Opher , Levanon Keren , Yam Einav Nili-Gal 
Published: March 2023

Abstract
Introduction: Patients younger than 50 years old with node negative hormone receptor (HR) positive her2 negative breast cancer and oncotype Dx recurrence scores (RS) under 16 do not benefit from adjuvant chemotherapy. Those with a RS between 16-25 may have a marginal benefit from the addition of adjuvant chemotherapy, however a similar benefit may be achieved with adjuvant ovarian function suppression (OFS). The aim of this study is to describe real world treatment patterns and outcomes of premenopausal node negative patients with low and intermediate RS, with an emphasis on adjuvant OFS, endocrine therapy (ET), and menopausal status during adjuvant treatment. Methods: We retrospectively reviewed the records of all node negative patients under 50 years old who were sent for oncotype testing between 2008 and 2018. One hundred and sixty-five patients with low or intermediate RS were included in our analysis. Continuous variables were described using medians and interquartile range (IQR). Categorical variables were described as frequencies and percentages. Differences between categorical variables were analyzed with the chi squared test and survival was analyzed using the Kaplan-Meier method. The cox proportional hazards model was used to test the effect of multiple factors on survival. Breast cancer specific survival (bcss) was defined as the time to first breast cancer recurrence (local recurrence, second breast cancer, distant recurrence) and distant disease-free survival (ddfs) was defined as the time to any distant recurrence. Results: The median age was 44 (41-47) and median RS was 17 (14-20). Median follow-up time was 82 (61-108) months. One hundred and three (62.4%) patients had low clinical risk as defined in TailorX and 136 (82.4%) had intermediate RS. Fourteen (8.5%) patients with nodal micrometastases were also included. Only 5 (3%) patients received adjuvant chemotherapy and 74 (44.8%) received adjuvant OFS. Of the 91 (55%) of patients who did not received OFS, 21 (23%) went into menopause or underwent subsequent oopherectomy while on adjuvant ET. One hundred and three (62.4%) patients received adjuvant tamoxifen alone, 16 (9.7%) received an aromatase inhibitor alone, and 40 (24.2%) underwent an endocrine switch with all but 1 beginning treatment with tamoxifen. There were no significant differences in clinical risk or RS risk group between patients that received and did not receive OFS. There were 22 (13.3%) bcss recurrences. Twelve (7.2%) patients had a local recurrence, 5 (3%) patients had second breast cancers, and 5 (3%) had a distant recurrence as their first recurrence. Overall, only 6 (3.6%) patients had a distant recurrence. Both OFS and ET type were not significantly associated with bcss or ddfs. On univariate analysis menopause during ET was significantly associated with improved bcss (HR= 0.2, 95% CI 0.05-0.85), however on multivariate analysis it was no longer significant. Conclusion: With only 6 (3.6%) distant recurrences over a median follow-up of over 6.5 years node negative premenopausal women with low or intermediate RS treated in our institution show an excellent prognosis regardless of treatment type. Our results support the evidence that most of these patients do not need chemotherapy and suggests that most patients do not require OFS as well. Additional data examining the relationship between gene expression profiles and OFS benefit are needed to help guide OFS treatment in premenopausal patients who do not require chemotherapy.
Citation Format: Opher Globus, Keren Levanon, Einav Nili-Gal Yam. Real world treatment of node negative low and intermediate recurrence score breast cancer [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 P2-03-06.