Association of intrathecal trastuzumab to standard therapy in patients with leptomeningeal metastasis in HER2 positive breast cancer.

Abstract

e13021 Background: Leptomeningeal metastases are rare but fatal manifestation of metastatic breast cancer, especially in HER2 positive sub-type, with limited treatment options and median overall survival in the range of only 4-6 weeks in untreated patients. Methods: Our prospective study included 9 patients with HER2 positive breast cancer with leptomeningeal metastases that received intrathecal treatment with Trastuzumab along with systemic therapy. Data was compared with a control lot of 9 patients with leptomeningeal metastasis that did not receive intrathecal treatment. Radiotherapy was administered in all patients. The patients included in the study received cures of 150 mg of Trastuzumab injected intrathecal every 3 weeks. Results: Median age of the patients at the time of diagnosis was 53 years. Median time from diagnosis of BC until diagnosis of leptomeningeal carcinomatosis was 3.4 years. Median progression free survival for patients receiving trastuzumab intrathecal was 11.1 months compare with 6.4 months in patients receiving standard treatment, p < 0.019. In our lot of patients, response rate was 66.6%. A clinical benefit with symptoms relief was observed in 77.7% of patients. Mean number of administrations was 12. Two patients presented pain and in two instance the administration was not possible. Concurrent systemic treatment consisted in lapatinib and capecitabine (22.2%), trastuzumab emtansine (44.5%), tucatinib combination (22.2%), vinorelbine (11.1%) and no unexpected toxicity to systemic treatment was noticed. Conclusions: Intrathecal administration of trastuzumab along with systemic treatment and radiotherapy, might improve or stabilise the consequences of leptomeningeal involvement by HER2-positive breast cancer with manageable toxicity.