Abstract PS1-04-05: Incidence of relationship breakups during endocrine therapy for breast cancer: preliminary results of the ReBreCa trial

Abstract Background: Breast cancer and its treatment significantly impact patients' interpersonal relationships, with lasting effects. Adverse events of anticancer therapies, including sexual dysfunction and body image changes, frequently negatively affect patients' quality of life and relationships. This study aimed to evaluate the incidence of relationship breakups (RBr) during endocrine therapy (ET) for breast cancer and its associated factors. Methods: This is a single-center, retrospective, observational cohort study. Participants were female ≥18 years-old, with hormone-receptor positive (HR+) breast cancer (metastatic or non-metastatic, including in situ neoplasia) undergoing ET for at least 6 months. Data were collected through an online questionnaire, which included demographic, relationship and quality of life aspects, and electronic medical records. The patients who reported being in a relationship at ET initiation were included in the primary outcome analysis. The primary endpoint was the incidence of RBr among those in a relationship at ET initiation. Secondary endpoints included factors associated with RBr and motivations for maintaining relationships. Descriptive statistics were used for describing the population characteristics and the endpoints. Chi-square or Fisher's exact tests were used for determining categorical variables association. Results: Of 201 patients who completed the questionnaire, 162 were in a relationship at ET initiation, and were included in the primary analysis. The median age at diagnosis was 44 years-old (range: 26-71), and the majority worked outside home (74.1%), had at least higher education (86.4%), had children (72.8%), were premenopausal (75.9%) and overweight (67.9%). 13.6% had HER2+ tumors, 14.8% metastatic disease, and 6.8% in situ carcinomas. The ETs in use were: SERMs (23.5%), aromatase inhibitors (70.4%), and SERDs (6.2%). 58% received ovarian function suppression and 24.7% a target-therapy (24.1% iCDK4/6). 95.1% were heterosexual, 3.1% homosexual and 1.9% bisexual. 72.2% were married. Sixty-two (38.3%) reported a RBr after at least 6 months of ET. Among those, 35.4% (n = 22) attributed the RBr to cancer treatment in general, and 27.4% (n = 17) to ET. The RBr decision was made by the patient in 48.1% (n = 13), by the partner in 37% (n = 10), and by both in 14.8% (n = 4). Some contributing factors to RBr were low libido (27.0%), sexual dissatisfaction (19.0%), prejudiced body image (22.2%), and difficulties in communication (20.6%). Only axillary node dissection was associated with RBr in univariate analysis (52.3% vs 33.3% for sentinel lymph node dissection; p = 0.04). There was a trend of association between nulliparity and RBr (50% vs 33.9%; p = 0.07). Despite 55.6% of responders referring to a conflictual RBr, 74.1% of patients who ended their relationships expected a lasting relationship in the future. Considering the 100 women who maintained their relationships, only 14% were dissatisfied with them. The main contributing factor for maintaining the relationship was affection (73%), with children (8%), financial aspects (2%), religion (2%), fear of loneliness (2%) and others (3%) being less relevant. Conclusion: Our findings reveal a considerable incidence of RBr among breast cancer patients undergoing ET, with more than one third of patients directly attributing the ending of the relationship to treatment. Factors such as libido, sexual satisfaction, body image, and communication were reported as crucial in this context of relationship vulnerability. This study underscores the urgent need to integrate psychosocial assessments and to offer targeted support to manage the impacts of ET/treatment on patients' relational lives, aiming to preserve well-being and quality of life during and after breast cancer treatment. Citation Format: M. C. Carvalho, M. G. Cesca, I. d. Oliveira, B. C. Figueroa, T. C. Lima, S. M. Sanches, V. C. Lima, R. P. Souza. Incidence of relationship breakups during endocrine therapy for breast cancer: preliminary results of the ReBreCa trial [abstract]. In: Proceedings of the San Antonio Breast Cancer Symposium 2025; 2025 Dec 9-12; San Antonio, TX. Philadelphia (PA): AACR; Clin Cancer Res 2026;32(4 Suppl):Abstract nr PS1-04-05.