P11.61.B Capecitabine treatment of CNS metastases from breast cancer: intracranial response and survival

Abstract Background 20-30% of breast cancer patients develop brain metastases (BM) and 5% leptomeningeal metastases (LM). Incidence of BM and/or LM is dependent on breast cancer subtype. Treatment of BM consists of local treatment (resection and/or radiotherapy) and if possible systemic therapy. LM can be treated with radiotherapy of the symptomatic location of the nervous system and/or systemic therapy. Capecitabin is effective for both systemic metastases and BM of HER2-positive breast cancer. The effect of capecitabine in the non-HER2-positive breast cancers and in the LM group is largely unknown. The goal of this study is to determine the intracranial response of capecitabine and survival in HM and/or LM of the various breast cancer subtypes. Material and Methods breast cancer patients with HM and/or LM treated with capecitabine were selected retrospectively from a breast cancer patient cohort treated at the Netherlands Cancer Institute - Antoni van Leeuwenhoek between 2005 and 2020. Follow-up MRI scans of the brains were performed in all patients. The primary endpoints were intracranial response, intracranial progression-free survival (PFS) and overall survival (OS). Subgroup analyses for breast cancer subtypes and BM and LM patient groups were done. Results 93 of 381 patients treated for CNS metastases of breast cancer fulfilled the inclusion criteria. Sixty-one patients (66%) had HM only, 13 (14%) had LM only and 19 patients (20%) had both HM and LM. Forty-six percent of patients had HER2-positive breast cancer, 26% had hormone receptor-positive breast cancer and 28% of patients had a triple negative subtype. After three months of capecitabine treatment intracranial response was 53%. Median OS in the patient group with intracranial response was 16.5 months versus 4.5 months in the non-response group. The hazard ratio (HR) for the median OS, corrected for radiotherapy and concurrently administered, other systemic therapy was 0.33 (95% CI: 0.17-0.67). Median intracranial PFS was 7.3 months in the response group versus 1.4 months in the non-response group (p