Background: Oncologists struggle to know which patients are near the end of life to enable timely transitions to supportive care. We developed and validated a breast cancer-specific prognostic tool for near-term death using electronic health record data from CancerLinQ Discovery, a national oncology database. In our prior work, oncology clinicians described the tool as potentially beneficial in considering whether to continue cancer-directed treatment, providing prognostic information to patients who want it, planning for supportive care, and guiding patient conversations. To prepare for implementation of the tool in usual care, we sought to understand the perspectives of patients with metastatic breast cancer (MBC) and caregivers regarding discussions of prognosis and use of the tool. Methods: We identified patients with MBC and caregivers through the UNC Breast Oncology Clinic. We conducted in-depth, semi-structured interviews by phone to assess participant beliefs and experiences about discussing prognosis with their oncologist and potential benefits and harms of using the tool in usual care. Interviews were audio recorded and transcribed, and data were analyzed using a coding-based thematic analysis. Results: We conducted 19 in-depth interviews (11 patients and 8 caregivers) from July 2022 to February 2023. Patients and caregivers had varying preferences for conversations regarding prognosis, ranging from not wanting to discuss prognosis to identifying preferences for the content and timing of these conversations. Perceived benefits of a prognostic tool included helping them make decisions about more cancer treatment versus increased supportive care, signaling the need for more end-of-life resources, decreasing uncertainty, and helping plan for the future. Among patients and caregivers who perceived risks of the tool, most identified general concerns related to discussions of prognosis, including provoking anxiety, signaling for a patient to “give up,” and suggesting to a patient their clinician had given up. Others identified specific concerns about the tool, including the possibility of receiving incorrect information. Conclusions: Implementation of a prognostic tool for near-term death from advanced breast cancer into routine clinical care must consider the perspectives of patients and caregivers with different preferences for prognostic information. Objections to use of the prognostic tool centered on beliefs regarding the appropriateness of prognostic discussions overall, rather than the specific role the tool would play in the discussion. Next steps include studying how to elicit patient and caregiver preferences for prognostic information in the clinic and how to help oncologists initiate serious illness conversations and utilize this prognostic tool in a way that aligns with patient and caregiver preferences.