LINAC Radiosurgery for Patients with a Limited Number of Brain Metastases

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Abstract

Patients (pts) with brain metastases have a high risk of cancer-related death due to extra- or intracranial tumor manifestations. The present retrospective analysis demonstrates the ability of linear accelerator (LINAC)-based radiosurgery to control intracranial disease and prolong survival in pts with one to three metastases. From 1991 to 1996, 106 pts (42 females, 64 males; median age, 57 years) with cerebral metastases were treated by stereotactic radiosurgery with a LINAC (8 MeV) equipped with tertiary collimators. In 70 pts, a single metastasis was present; 36 pts had two or three metastases. Fifty-nine pts were treated for their first occurrence of brain metastases; 47 pts had been treated prior to radiosurgery by resection and/or whole-brain irradiation. Histology of the primary tumor was non–small cell lung cancer (36 pts), melanoma (20 pts), breast cancer (15 pts), hypernephroma (15 pts), and other (20 pts). All together, 157 metastases (0.04–69.0 ml; median, 2.7 ml) were irradiated with marginal doses of 12–25 Gy (median, 20 Gy) referred to the 65–80% isodose. Seventy-two percent of the lesions were treated with a single isocenter. Adjuvant whole-brain irradiation was applied in six pts. One hundred thirty-five of 157 metastases were evaluated for response: complete response (CR), 24%; partial response, 31%; no change, 30%; and progression of disease, 15%. CR rates were highest (48%) in small metastases (<1-cm diameter), independent of histological type and dose. The overall median survival was 8 months. Multivariate Cox regression analysis revealed a significant impact on survival for Karnofsky performance score, presence of extracranial tumor, and volume of largest metastasis. Freedom from neurological death was determined only by the volume of the largest metastasis. Patients with multiple metastases and/or extracranial disease had a higher risk of developing new outfield brain metastases. Due to salvage therapy (second or third course of stereotactic radiosurgery, whole-brain irradiation, surgery), the overall survival in pts with two or three metastases did not significantly differ from that in pts with single metastases. LINAC-based stereotactic radiosurgery in pts with up to three cerebral metastases results in survival rates approaching those of pts with resected single brain metastases. As pts with both single and multiple metastases can effectively be salvaged after receiving radiosurgery, extracranial tumor activity becomes a major determinator of survival.

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