Abstract P3-05-10: Disease features, genomic profiles and outcomes of younger vs. older Chinese hormone receptor positive (HR+), HER2 negative (HER2-) metastatic breast cancer (MBC) patients
Authors: Wang Jinhao , Liu Yaxin , Shao Bin , Dong Hang , Zheng Tiantian , Du Pan , Jia Shidong , King Bonnie , Wang Jing , Liu Xiaoran , Li Huiping 
Published: March 2023

Background: Breast cancer in younger women has been characterized as a more aggressive disease with relatively poor outcomes compared to breast cancer in older women. This pattern has been attributed to a variety of clinicopathologic characteristics including the enrichment of aggressive HER2+ and TNBC subtypes in younger patients. However, similar to older breast cancer patients, the majority of young breast cancer patients are HR+/HER2-. Here we have evaluated the clinicopathologic characteristics and genomic profiles of real-world HR+/HER2- MBC patients to examine the determinants of outcome for younger vs. older patients in this subtype. Patients and Methods: This study included 65 Chinese patients presenting with HR+/HER2- MBC at the Peking University Cancer Hospital. Blood samples were collected upon metastatic disease diagnosis before treatment and profiled with the targeted 152-gene PredicineCARETM sequencing panel. Fourteen patients were &lt; 40 years, 19 were 40-50 years, and 32 were &gt; 50 years at the time of primary cancer diagnosis. Kaplan-Meier survival analysis was performed to analyze outcomes including overall survival (OS), disease free survival (DFS) and progression free survival (PFS) in association with clinicopathologic and genomic variables. OS was also evaluated in association with age in separate multivariate models using Cox proportional hazards regression. Results: Significant variation across age groups was observed for several clinicopathological features, including molecular subtype classification (p = 0.045), de novo Stage IV disease (p = 0.011), type of adjuvant endocrine therapy (p = 5.56E-06), resistance to adjuvant endocrine therapy (p = 0.015) and receipt of adjuvant chemotherapy (p = 0.042). Luminal B status was most frequent in patients &lt; 40 years (92.31%), whereas de novo Stage IV disease was more prevalent in patients &gt; 50 years (37.5%). Aromatase inhibitors (AIs) were administered as adjuvant endocrine therapy (ET) to 73.68% of women &gt; 50 years vs. 16.67% and 0% of women aged 40-50 years and &lt; 40 years, respectively. Resistance to adjuvant ET was observed in 23.08% of patients &lt; 40 years but was not observed in the other age groups. Adjuvant chemotherapy was received by a higher proportion of patients in the 40-50 year age group (94.44%) compared to patients &lt; 40 years (69.23%) and patients &gt; 50 years (60%). No differences in somatic gene alteration frequencies were observed across age groups, menopausal status, germline mutation status or tumor grade. However, a higher frequency of FGFR1 alterations was observed in patients classified as Luminal B vs. A (p = 0.048). Comparison of profiles across women who received adjuvant ET revealed a higher prevalence of FGFR1 (p = 0.012), ATM (p = 0.047) and CCND2 (p = 0.04) alterations in patients treated with AIs vs. SERMS. In addition, a higher frequency of APC alterations was observed in patients with high (≥ 20%) vs. low (&lt; 20%) Ki67 index (p = 0.035). At the univariate level OS was significantly associated with age (p = 0.039). OS was shortest in patients &gt; 50 years, intermediate in patients &lt; 40 years, and longest in patients 40-50 years. Across all patients, shorter OS was also associated with de novo Stage IV disease (p = 0.0001), Luminal B subtype (p = 0.008), adjuvant ET with AIs vs SERMS (p = 0.028) and the presence of an FGFR1 (p = 0.028) or CCND2 (p = 0.033) alteration. In multivariate analyses, OS remained significantly longer for patients aged 40-50 years after adjustment for de novo Stage IV disease, Luminal B subtype and FGFR1 status (all p &lt; 0.05). Conclusions: In this group of real-world HR+/HER2- MBC breast cancer patients, younger age was not associated with worse outcomes. While current guidelines recommend treatment decisions based on tumor biology rather than age, young HR+ breast cancer patients are more likely to receive chemotherapy. Our findings support the development of biomarker-driven treatment strategies for these patients.

Citation Format: Jinhao Wang, Yaxin Liu, Bin Shao, Hang Dong, Tiantian Zheng, Pan Du, Shidong Jia, Bonnie King, Jing Wang, Xiaoran Liu, Huiping Li. Disease features, genomic profiles and outcomes of younger vs. older Chinese hormone receptor positive (HR+), HER2 negative (HER2-) metastatic breast cancer (MBC) 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 P3-05-10.