Stereotactic radiotherapy (SRT) with maintenance systemic therapy vs. standard-of-care (SOC) systemic therapy for oligoprogressive ER-positive, HER2-negative breast cancer (AVATAR-II).

Abstract

Purpose/Objective(s): The AVATAR I Trial demonstrated that oligoprogressive luminal (ER positive, HER2 negative) advanced breast cancer patients undergoing established first-line systemic therapy for metastatic disease benefited from SRT as second-line therapy along with their original systemic treatment. A modified PFS, defined as a disease progression not amenable to SRT treatment, was reported as 10.4 months. Given this result, this trial in progress seeks to assess if SRT combined with systemic therapy CDK4/6 inhibitor and Aromatase Inhibitor (CDK4/6+AI) can improve the Quality of Life (QoL) for this cohort of patients. Materials/Methods: AVATAR II is a Phase 2 randomized control trial that enrolls patients with advanced luminal breast cancer who have received first-line systemic treatment in the metastatic setting with a CDK4/6+AI. Patients require at least 1 extracranial oligoprogressing lesion amenable to SRT. Patients who had chemotherapy for metastatic disease, leptomeningeal disease, or prior radiotherapy to an oligoprogressing lesion were excluded. Patients were randomized to Arm A; SRT to all oligoprogressing lesions and continue CDK4/6+AI systemic therapy or Arm B; no SRT and review to assess if a change in systemic therapy is required. If a patient subsequently progresses, further SRT was permitted to delay a change in systemic therapy in patients who had received SRT as part of the trial. At 3-monthly reviews, patient reported outcomes are measured using the EORTC QLQ C30 and FACT-B forms. The trial is expected to recruit 74 patients. The primary endpoint is the area under the curve (AUC) of the Quality of Life/Global Health Status score from the EORTC QLQ-C30 from baseline to the 12-month follow-up visit. The secondary endpoints are to determine Progression-free Survival (PFS) and PFS 2, defined as the time from randomization to the date of first and second evidence of progression, respectively. Other secondary endpoints include ST-PFS, defined as randomization to the first evidence of progression requiring change in systemic therapy, Overall Survival, treatment-related toxicity and further QoL assessment using AUC of the FACT-B Total score from baseline to 12 months. Result(s): TBD. Conclusion(s): Assessing quality of life (QoL) is integral to evaluating the overall impact of cancer treatment. AVATAR II aims to demonstrate that by delaying a change in systemic therapy and potentially more potent side effects, receiving SRT at this stage in a patient's treatment paradigm will have a more positive impact on patients' QoL.Copyright © 2024