NCMP-03. INTRATHECAL TRASTUZUMAB TREATMENT OF HER-2 POSITIVE LEPTOMENINGEAL BREAST CANCER: THE UNIVERSITY OF MICHIGAN EXPERIENCE

Abstract

Abstract PURPOSE Breast cancer is the most common solid tumor to metastasize to the leptomeninges, affecting up to 5% of breast cancer patients. Overall survival for patients with leptomeningeal metastases (LM) is poor, with median survival of 4–6 months following diagnosis. There is limited data available on the efficacy of intrathecal (IT) trastuzumab in the treatment of Her-2 positive LM. METHODS A total of 30 patients with Her-2 positive breast cancer with LM treated at the University of Michigan from 2008–2020 were identified retrospectively. Of these, 13 patients were treated with IT trastuzumab beginning in June 2010 and followed through April 2020. Initial dose was 50–80 mg twice weekly for a minimum of 4 weeks, followed by slow taper. The 17 patients with Her-2 positive breast cancer with LM who did not receive IT trastuzumab served as control. RESULTS The median age of patients in the treatment group was 42 and 52 in the control group. Whole brain radiation therapy was received by 92% of patients in the treatment group and 76% in the control group. The median overall survival from diagnosis of LM to death was 20 months (interquartile range [IQR] 13–60 months) in the treatment group and 6 months (IQR 2–17 months) in the control group. Survival at 3 years and 5 years was 40% and 13%, respectively for the treatment group and 8% and 0% (no data available at 60 months), for the control group. Hazard ratio for death with IT trastuzumab 0.38 (95% CI 0.16–0.91, p=0.024). IT trastuzumab was overall well-tolerated (one patient developed meningitis, while another had shunt malfunction necessitating removal of the reservoir). CONCLUSIONS Patients with HER2+ LM who received IT trastuzumab demonstrated significantly improved OS compared to control with minimal toxicity.