Dose optimization and indication of linac radiosurgery for brain metastases

Purpose: The authors have examined treatment effects of linear accelerator based radiosurgery for brain metastases. Optimal doses and indications were determined in an attempt to improve the quality of life for terminal cance r patients. Methods and Materials: Ninety-two patients with 162 lesions were treated wi th Linac radiosurgery for brain metastases between April 1993 and September 1998. To determine prognostic factors, risk factors for recurrence, and ap pearance of new lesions, univariate and multivariate analyses were performe d. To compare the local control between the high-dose (mininum dose greater than or equal to 25 Gy: prescribed to the 50-80% isodose line) and low-dos e (minimum dose <25 Gy) irradiated groups, matched-pairs analysis was perfo rmed. Results: Median survival time was 11 months. In univariate analysis, extrac ranial tumor activity (p < 0.001) and Karnofsky Performance Status (KPS) (p = 0.036) were two significant predictors of survival. In multivariate anal ysis, the status of an extracranial tumor was the single significant predic tor of survival (p = 0.005). Minimum dose was the single most significant p redictor of local recurrence in univariate, multivariate, and matched-pairs analyses (p < 0.05). As to the appearance of new lesions, activity of extr acranial tumors was a significant predictor (p < 0.05). Side effects due to radiosurgery were experienced in 4 of 92 cases (4.3%). Conclusions: We concluded that brain metastases patients should be irradiat ed with greater than or equal to 25 Gy, when extracranial lesions are stabl e and longer survival is expected. Combined surgery and conventional radiat ion may have little advantage over radiosurgery alone when metastatic brain tumors are small and extracranial tumors are well controlled. When extracr anial tumors are progressive, the rate of appearance of new lesions in othe r nonirradiated locations becomes higher. In such cases, careful follow-up is required and a combination with whole brain irradiation should be consid ered. (C) 1999 Elsevier Science Inc.