Prospective study of stereotactic radiosurgery without whole brain radiotherapy in patients with four or less cerebral metastases: incidence of locoregional relapse and salvage radiotherapy

Abstract

Purpose/Objective: In this prospective cohort we evaluated time to first cerebral event (new metastatic lesion or relapse), time to WBRT after SRS, and survival in the patients with four or less brain metastases treated with SRS alone. Materials/Methods: Between January 1998 and September 2001, forty-one patients with cerebral metastasis underwent SRS using a dedicated linear accelerator. Inclusion criteria for enrollment were: patients with four or less metastatic brain lesions, age 18 years or older, biopsy proven cerebral metastases or CT/MRI of the brain consistent with metastatic lesions, lesions appropriate for treatment with SRS, life expectancy more than three months, and Karnofsky Performance Score (KPS) of 60 or more. Patients with small cell lung cancer or lymphoma and patients who elected to have WBRT were excluded from the study. Lesions were encompassed by a median 90% isodose line (range: 70–90%) with a single fraction of 1200–1800 cGy (median 1800 cGy). Median age at time of SRS was 55 years (30–75), and median KPS was 90 (60–100). The median number of lesions was 1 (1–4). Follow-up ranged from 1.5 to 31 months (median 7). Results: All patient data was available for analysis. Ten patients (24.3%) had local relapse at the treated site. Recurrences occurred inside the SRS treated volume in three patients and inside and outside in seven patients. Additionally, fourteen patients developed new lesions outside the SRS treated volume alone. Median time to intra-cerebral event was 4.25 months (1–24.6) within the subgroup of patients with progressive disease. Salvage radiation was given in 21 patients (51.2%). Only 12 of these 21 patients received WBRT because of multiple new lesions. The median time to WBRT after SRS was 4.85 months (1–12.7). Nine patients underwent additional SRS at median time of 5 months after the first treatment. The median survival (Kaplan-Meier) in all patients was 10 months (1–31). At time of last follow up, 16 patients (39%) were still alive. Conclusions: In our patients who were treated using SRS without WBRT, less than one-third have relapsed to date with multiple lesions requiring WBRT. Less than 25% have required retreatment with SRS. In those who developed progressive intracranial disease, median time to locoregional relapse was short (4.25 months); however, this should be kept in proportion with median survival in multiple RTOG trials for brain metastases of only 4–6 months.