Background: Use of patient-reported outcomes (PRO) to evaluate symptoms improves clinical outcomes. Best practices for implementing PROs into routine care may vary according to clinical scenario, site-specific resources and programmatic goals. Patients with metastatic breast cancer (MBC) often experience a variety of symptoms. Methods: As a quality improvement project, we are pilot testing incorporation of a battery of PRO measures into routine care for patients with MBC at Johns Hopkins in order to gain experience that will guide future broader implementation of PROs across our program. Participants complete the PROs on paper at baseline (BL), 3, and 6 months (mo). Measures include NCCN Distress Thermometer (BL only), Patient Health Questionnaire-8 (PHQ-8), Generalized Anxiety Disorder-7 (GAD-7), PRO-CTCAE Insomnia questions and a modified version of the revised Edmonton Symptom Assessment System (r-ESAS) questionnaire with 3 extra symptom domains. Project team members alert clinicians by email of scores that exceed severity thresholds as follows – Distress: ≥4, PHQ-8: ≥8, GAD-7: ≥10, any item on r-ESAS: ≥4 and PRO-CTCAE Insomnia: severe/very severe or quite a bit/very much. Results: From May 29, 2020 and April 5, 2021, 67 patients were approached for participation, and 40 (59.7%) completed the BL PROs. Median age was 64 (range 36-85). Most participants were White (70%), non-Hispanic (90%) and had hormone receptor-positive (93%) MBC. At BL, 22 (55%) had visceral disease and most were receiving endocrine-based regimens [21 (53%)] or chemotherapy [16 (40%)]. 27 (68%) participants had ≥1 BL alert. The most common BL alerts were for symptoms on the r-ESAS [23 participants (58%)]. The most frequent items on the r-ESAS for which participants had BL alerts were pain, tiredness, well-being, tingling/numbness and rash. Other BL alerts were: Distress [9 participants (23%)], PRO-CTCAE Insomnia [5 participants (13%)], PHQ-8 [4 participants (10%)] and GAD-7 [2 participants (5%)]. To date, 24 of 35 (69%) and 15 of 28 (54%) participants who have reached the 3 and 6 mo time points have completed the respective follow-up (FU) PROs. Most common FU alerts to date are on the r-ESAS [3 mo: 14 participants (58%), 6 mo: 9 participants (60%)]. The project team has successfully notified providers of all alerts to date. Clinical actions (phone calls, provider visits and/or referrals) have been taken within 30 days of notification for > 75% of alerts. Conclusions: Implementation of a PRO battery for patients receiving routine care for MBC led to detection of a range of symptoms, the majority of which were clinically actionable. Restrictions on in-person interactions during the COVID-19 pandemic may have contributed to low rates of PRO completion in this pilot project. Prior to broader implementation, we will consider strategies such as an electronic platform and a shorter battery to enhance patient engagement.