Clinical Outcomes of Breast Cancer Brain Metastases Treated with Stereotactic Radiation and Capecitabine

Abstract

Capecitabine is often used as a radiosensitizer in combination with external beam radiation therapy. However, relatively little is known about the safety and efficacy of combined treatment with capecitabine and stereotactic radiation for the treatment of brain metastases. In this study, we assess our institutional experience in treating breast cancer brain metastases (BCBM) with stereotactic radiation and capecitabine. This is a retrospective study of 23 consecutive patients with BCBM who received 31 stereotactic radiation sessions to 90 lesions from January 2005 to November 2019 with capecitabine delivered within 6 months of stereotactic radiation. Patient, tumor, and treatment characteristics were retrieved from the clinical chart. The Kruskal-Wallis and Pearson’s chi-square tests were used to test differences between cohorts as appropriate. The Kaplan-Meier method was used to calculated overall survival (OS), local control (LC), and distant intracranial control (DIC) from the date of SRS. There were 21 patients diagnosed with invasive ductal carcinoma, 1 patient with invasive lobular carcinoma, and 1 patient with metaplastic carcinoma. Nine, 10, and 9 patients had ER-positive, PR-positive, and HER2-positive disease, respectively. Fourteen patients were originally diagnosed with de novo metastatic breast cancer. Median follow up time from stereotactic radiation was 9 months (1.8 to 92.8). The median age at the time of stereotactic radiation was 51 years (40 to 75). The median number of brain metastases at presentation was 2 (1 to 12), and the initial treatment at the time of brain metastasis included stereotactic radiation (65.2%), WBRT (26.1%), and surgery with post-operative radiotherapy (8.7%). Ten lesions were treated with fractionated stereotactic radiation (FSRT) to a median prescription dose of 25 Gy (24 to 30 Gy) delivered in 3 to 5 fractions, and 80 lesions were treated with stereotactic radiosurgery (SRS) to a median prescription dose of 21 Gy (15 to 24 Gy) in a single fraction. The median planning treatment volume was 0.71cc (0.012 to 34cc). Of the 90 treated lesions, 40 (44.4%) were treated with concurrent capecitabine. The 1-year OS, LC, and DIC were 46%, 95%, and 32%, respectively. There was 1 case (1.1%) of symptomatic radiation necrosis. There were 2 cases of leptomeningeal progression. We demonstrate that stereotactic radiation and capecitabine is a well-tolerated treatment for BCBM with high LC and a low associated risk for symptomatic radiation necrosis.