Abstract PO2-17-03: Patient reported outcomes (PROs) and survival with toremifene versus aromatase inhibitors (AI) in patients with moderate/high-risk premenopausal hormone receptor (HR)-positive breast cancer: A real-world study

Abstract Background: The selective estrogen receptor modulator (SERM) toremifene, a synthetic analogue of tamoxifen, has shown similar efficacy to tamoxifen in patients with HR-positive breast cancer and is widely used in China for the treatment of premenopausal women with breast cancer. Multiple studies have confirmed the benefit of ovarian function suppression (OFS) combined with AI and SERMs in premenopausal women with HR-positive breast cancer. However, to date, there are no data comparing the efficacy and safety of toremifene plus OFS versus AI plus OFS. In this real-world study, we compared PROs and survival with toremifene or AI combined with OFS in patients with moderate/high-risk premenopausal HR-positive breast cancer. Methods: We enrolled premenopausal female patients with HR-positive, moderate/high-risk breast cancer who received OFS combined with toremifene or AI between January 1, 2010 and December 31, 2017 at the Breast Cancer Center of Sun Yat-sen Memorial Hospital. The primary endpoint was PROs, which were collected from January 1 to March 31, 2023, including the SF-36 and five-level EuroQol five-dimensional (EQ-5D-5L) questionnaires. Disease-free-survival (DFS) and safety were secondary endpoints. Associations between treatment group and SF-36 scores were evaluated using a Student’s t test and between treatment group and EQ-5D-5L scores using nonparametric tests. DFS was assessed using the Kaplan–Meier method and Cox regression. Results: A total of 392 patients were enrolled; 171 (43.6%) received toremifene and 221 (56.4%) received AI. Mean ± standard deviation scores for the role physical and general health dimensions of SF-36 were higher in the toremifene group versus the AI group (7.44±1.21 vs 7.15±1.48, P=0.034 and 22.90±3.95 vs 21.78±4.33, P=0.009, respectively). Scores on the anxiety/depression (AD) dimension of EQ-5D-5L were significantly different between the toremifene and AI treatment groups (mean rank: 184.14 vs 206.07, P=0.038); ‘no problems’ was selected by 49.7% and 37.1% of patients in the toremifene and AI groups, respectively. There were no significant differences in the other dimensions of SF-36 and EQ-5D-5L between the toremifene and AI groups (P>0.05). Similar estimated 5- and 8-year DFS rates were reported for the toremifene and AI groups; 96.5% (95% CI: 93.7-99.2) and 91.9% (95% CI: 88.2-95.5), and 87.4% (95% CI: 81.1-93.8) and 87.8% (95% CI: 81.1-94.4), respectively, and the hazard ratio for DFS was 0.75 (95% CI: 0.38-1.46), P=0.39. DFS was also comparable in the two treatment groups when stratified by HER2 status, age (≤40y vs >40y) and estrogen receptor expression level (≤20% vs >20%). Adverse event rates were generally similar in the two treatment groups, except for a higher rate of endometrial thickening (17.5% vs 1.8%, p< 0.001) and a lower rate of morning stiffness (7.6% vs 14.5%, p< 0.001) in the toremifene versus the AI group. Conclusion: Patients who received toremifene plus OFS had better role physical and general health dimensions on SF-36 and AD dimensions of EQ-5D-5L than those receiving AI plus OFS. There were no significant differences in 5- or 8-year DFS between the toremifene and AI groups. Both treatments were generally well tolerated. Citation Format: Yaping Yang, Fengxia Gan, Wenqian Yang, Yuan Xia, Qiang Liu, Chang Gong. Patient reported outcomes (PROs) and survival with toremifene versus aromatase inhibitors (AI) in patients with moderate/high-risk premenopausal hormone receptor (HR)-positive breast cancer: A real-world study [abstract]. In: Proceedings of the 2023 San Antonio Breast Cancer Symposium; 2023 Dec 5-9; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2024;84(9 Suppl):Abstract nr PO2-17-03.