RADIOSURGERY IN THE INITIAL MANAGEMENT OF MALIGNANT GLIOMAS - SURVIVAL COMPARISON WITH THE RTOG RECURSIVE PARTITIONING ANALYSIS

Purpose: To evaluate the impact of stereotactic radiosurgery on the su rvival of patients treated with malignant gliomas. Methods and Materia ls: A total of 115 patients from three institutions (75 from the Joint Center for Radiation Therapy, 30 from the University of Wisconsin, an d 10 from the University of Florida) were treated with a combination o f surgery, external beam radiation therapy, and linac-based radiosurge ry as part of similar institutional protocols from March 1988 through July 1993. Patients were stratified into six prognostic classes (class es 1-6) based on the recursive partitioning analysis of multiple progn ostic factors previously reported by the Radiation Therapy Oncology Gr oup. Results: The actuarial 2-year and median survival for all patient s analyzed was 45% and 96 weeks, respectively. In comparison to the re sults from a previously published analysis of 1578 patients entered on three Radiation Therapy Oncology Group external beam radiotherapy pro tocols from 1974 to 1989, those patients treated with radiosurgery had a significantly improved 2-year and median survival (p = 0.01) corres ponding with a standardized mortality risk ratio of 0.51 [95% confiden ce interval (CI): 0.31, 0.85]. This improvement in survival was seen p redominantly for the worse prognostic classes (classes 3-6). The 2-yea r survival for the radiosurgical patients compared with the previously reported patients was 81% vs. 76% for classes 1/2, 75% vs. 35% for cl ass 3, 34% vs. 15% for class 4, and 21% vs. 6% for classes 5/6, respec tively. Although Karnofsky performance status and prognostic class wer e significant on univariate analysis, only the Karnofsky score was a s ignificant predictor of outcome on multivariate analysis. Median and 2 -year survival for patients with a Karnofsky score greater than or equ al to 70 was 106 weeks and 51%, respectively, as compared to 38 weeks and 0% for patients with a Karnofsky score < 70% (p = 0.001). Conclusi ons: The addition of radiosurgery to conventional treatment (surgery a nd external beam radiotherapy) of malignant gliomas appears to improve survival when compared to historical reports. These results should be interpreted with caution because the recursive partitioning model doe s not completely predict the prognosis of the patients treated in the present study. Although this study suggests that radiosurgery may prol ong survival in patients with malignant gliomas, the role of radiosurg ery in the management of these patients remains to be defined by a pro spective randomized trial.