Gamma Knife Radiosurgery for Brain Metastases From Primary Breast Cancer

Abstract

Stereotactic radiosurgery (SRS), with or without whole brain radiotherapy (WBRT), is commonly used to treat brain metastases from breast cancer. However, the relative roles of SRS vs. WBRT remain undefined. It is also unclear whether size and number of metastases influence survival after SRS. We reviewed our SRS experience with brain metastases from breast cancer at the University of California, San Francisco in order to determine how size and number of metastases and omission of WBRT affected median survival time (MST) and freedom from progression (FFP). We retrospectively reviewed records of all patients treated with SRS from 1991–2005 to identify patients with brain metastases from breast cancer who underwent SRS with or without WBRT for newly-diagnosed or recurrent metastases. MST and FFP were calculated using the Kaplan-Meier method. Survival was measured from the date of brain metastasis diagnosis in patients with newly-diagnosed brain metastases. All other endpoints were measured from the date of SRS. Prognostic factors were evaluated with the log-rank test and Cox proportional hazards model. From 1991–2005, 175 consecutive patients underwent SRS for brain metastases from breast cancer. Excluding eight patients who had surgical resection of a brain metastasis prior to SRS, 91 patients had SRS with or without WBRT for newly-diagnosed brain metastases and 76 patients had SRS for recurrent brain metastases after prior WBRT. The median patient age at the time of SRS was 51 years (range, 25–83 years) and the median Karnofsky performance score was 90 (50–100); 17% of patients were RPA class 1, 79% class 2, and 4% class 3. The overall MSTs were 16.9 months among the 91 newly-diagnosed patients and 11.7 months for the 76 patients with recurrent brain metastases. Omission of upfront WBRT did not significantly affect MST (p = 0.14), median brain FFP (p = 0.63), or median freedom from new brain metastases (p = 0.77) in newly-diagnosed patients (Table 1). No association was found between number of treated brain metastases and survival time; in newly-diagnosed patients, the MSTs were 25.9, 13.9, 33.1, 16.9, and 17.6 months for patients with 1, 2, 3, 4–6, or >6 brain metastases (p = 0.31), while for patients with recurrent brain metastases the corresponding MSTs were 12.2, 11.6, 11.8, 7.4, and 13.4 months (p = 0.77). Multivariate analyses and outcomes allowing for salvage therapy will be presented. In this SRS series, the omission of WBRT did not affect MST or FFP in patients with newly-diagnosed brain metastases from primary breast cancer. For patients with newly-diagnosed or recurrent brain metastases, MST was not affected by the number of metastases treated.Table 1Endpoint (by patient)SRS alone initiallySRS + upfront WBRTSRS for recurrenceMedian survival19.5 mo16.3 mo11.7 mo1-year survival64%67%46%1-year local FFP79%77%52%Median FF new brain mets8.6 mo10.7 mo7.4 mo1-year FF new brain mets47%41%27%Median brain FFP8.0 mo10.0 mo6.2 mo1-year brain FFP38%30%14% Open table in a new tab