Abstract 4798: MRI screening for brain metastases (BrM) versus SYMptom-directed brain imaging for patients with triple negative (TN) or HER2+ metastatic breast cancer (MBC): An ad-hoc interim analysis of a randomized phase II pilot study

Abstract Background: Patients with HER2+ or TN MBC are at high risk of developing BrM, but the role of MRI screening for early detection of asymptomatic BrM has not yet been established. Methods: We conducted a multicentre phase II pilot study, which randomized patients with TN or HER2+ MBC to 1 year of BrM screening (contrast enhanced brain MRI at baseline, 4, 8, and 12 months) versus a control arm of symptom directed brain imaging (MRI only if symptoms of BrM develop). The primary goal was to determine the feasibility of a future randomized trial of BrM screening versus symptom-directed imaging in this patient population. Key inclusion criteria were age ≥18; TN MBC diagnosed ≤12 weeks prior to study entry or HER2+ MBC with no restrictions regarding time of diagnosis; no symptoms of BrM or known asymptomatic BrM; ECOG ≥ 1 and no MRI contraindications. Overall (EORTC QLQ BN20) and neurologic-specific (FACT-BR tools) quality-of-life as well as cancer-related anxiety (NCI PRO-CTCAE) were assessed at baseline, 6 and 15 months. Criteria rendering a future trial “not feasible” were defined a-priori as: 30% of eligible patients enroll in the study, 50% complete the study protocol, and/or 50% of patients allocated to the control arm during the 1 year study period are screened for asymptomatic BrM with CT or MRI. Results: Between 2018 and 2023, 44 patients from 3 participating centres enrolled in the study. Thirty-five participants (80%) had HER2+ and 9 (20%) had TN MBC. Of the 22 patients randomized to each of the study arms; 3 patients (8%) in each arm withdrew prior to study completion. Reasons for withdrawal included claustrophobia (n=3) or discontent with their randomised arm (n=3) or follow-up requirements (n=1). Metrics regarding the proportion of eligible patients who enrolled in the study were only collected from the Sunnybrook Odette Cancer Centre site; of 91 patients approached, 38 (42%) enrolled in the study. Within the 12-month study period, the incidence of BrM among patients in the screening arm was n=3 (14%) versus n=4 (18%) in the control arm. To-date among patients in the study arm, 11 (50%) completed the 12-month screening protocol, 5 (23%) remain on study and 6 (27%) did not complete the protocol due to either death or early study withdrawal. Among patients in the control arm, 10 (45%) completed 12-month follow-up, 4 (18%) remain on study and 8 (36%) did not complete follow-up due to either death or early study withdrawal. In total, 13 patients (59%) in the control arm had brain imaging, 4 in the absence of neurological symptoms. Conclusion: A large randomized trial to investigate the utility of MRI-based surveillance for asymptomatic detection of BrM in the proposed patient population is likely feasible, although episodic brain imaging in the control arm was common. Analysis of patient reported outcomes is ongoing. Citation Format: Katarzyna Joanna Jerzak, Megan Shum, Gregory Pond, Orit Freedman, Gursimran Chandhoke, Tatiana Conrad, Priscilla Brastianos, Gregory Stanisz, Arjun Sahgal, Ellen Warner. MRI screening for brain metastases (BrM) versus SYMptom-directed brain imaging for patients with triple negative (TN) or HER2+ metastatic breast cancer (MBC): An ad-hoc interim analysis of a randomized phase II pilot study abstract. In: Proceedings of the American Association for Cancer Research Annual Meeting 2024; Part 1 (Regular Abstracts) ; 2024 Apr 5-10; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2024;84 (6Suppl): Abstract nr 4798.