Abstract OT3-01-04: An open-label, single-arm, phase II study of pertuzumab with high-dose trastuzumab for the treatment of central nervous system progression post-radiotherapy in patients with HER2-positive metastatic breast cancer (PATRICIA)

Abstract

Abstract Background: Central nervous system (CNS) metastases are observed in up to half of patients with HER2-positive metastatic breast cancer (MBC), with incidence likely to continue to rise due to longer survival through improved systemic treatments. While radiotherapy-based approaches can be effective, there are potential short- and long-term toxicities, and patients frequently progress. CNS response to existing systemic therapies has been generally poor, and there is a high unmet need with no approved treatment for CNS metastases in HER2-positive MBC. Combination of the HER2-targeted monoclonal antibodies trastuzumab and pertuzumab provides a more comprehensive blockade of HER2 than either antibody alone, and data from the phase III CLEOPATRA trial suggest that adding pertuzumab to trastuzumab and docetaxel may delay onset of CNS disease. Trastuzumab concentrations in the CNS are increased under conditions of an impaired blood–brain barrier (BBB) and subtherapeutic levels in the CNS may be related to insufficient dosing rather than inability to cross the BBB. The PATRICIA trial is evaluating the addition of pertuzumab with high-dose trastuzumab to a patient's current systemic treatment for HER2-positive MBC patients with CNS progression post-radiotherapy and stable systemic disease. Study design: In this US-based, phase II, open-label, single-arm study, patients will receive intravenous pertuzumab (840 mg loading dose followed by 420 mg every 3 weeks) in combination with intravenous high-dose trastuzumab (6 mg/kg weekly) in addition to their current systemic therapy (except for ado-trastuzumab emtansine or lapatinib) until disease progression or unacceptable toxicity. Eligibility criteria: Patients aged ≥18 years with confirmed HER2-positive MBC with new and/or progressive CNS lesions >60 days after whole-brain radiotherapy or stereotactic radiosurgery for CNS metastases, performance status 0–1, and stable systemic disease will be eligible. Patients must have a baseline left ventricular ejection fraction (LVEF) ≥50%, no significant history of cardiac disease or current use of anthracyclines, life expectancy >12 weeks, and not be pregnant or lactating. Aims: The primary efficacy endpoint will be objective response rate (ORR) in the CNS, assessed by the investigator using RANO–BM criteria. Secondary endpoints will include duration of CNS response, progression-free survival (CNS and/or non-CNS), overall survival, and safety. Pharmacokinetic and patient-reported outcomes will also be evaluated. LVEF will be assessed throughout treatment and follow-up. An interim analysis will be performed when 15 patients have completed 2 cycles, and the study will be stopped if no clinical benefit (complete response, partial response, or stable disease in the CNS) is seen or if two or more patients have congestive heart failure events related to trastuzumab or pertuzumab. Statistical methods: The recruitment target is 40 patients; with 35 evaluable, the 95% confidence interval around an estimated ORR of 20% will be 8.4–36.9%. The trial opens for accrual in Q3 2015. Citation Format: Lin NU, Pegram MD, Lai C, Lacasia A, Stein A, Yoo B, Perez EA. An open-label, single-arm, phase II study of pertuzumab with high-dose trastuzumab for the treatment of central nervous system progression post-radiotherapy in patients with HER2-positive metastatic breast cancer (PATRICIA). [abstract]. In: Proceedings of the Thirty-Eighth Annual CTRC-AACR San Antonio Breast Cancer Symposium: 2015 Dec 8-12; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2016;76(4 Suppl):Abstract nr OT3-01-04.