[Prognostic factors for deep situated malignant gliomas treated with linac radiosurgery].

Background & Objective: Though radiosurgery has been used for more than 10 years, the value of radiosurgery for malignant glioma has not been clarified. This paper was designed to investigate efficacy of radiosurgery to malignant glioma by analyzing the prognostic factors affecting prognosis of malignant gliomas treated with linac radiosurgery.

Methods: Fifty-eight patients with deep situated malignant gliomas, 28 anaplastic astrocytomas(AA) and 30 glioblastomas (GBM), aged from 7 to 70 years, were analyzed. The mean volume of tumor was 12.08 cm3, and mean prescription dose for linac radiosurgery was 19.42 Gy. The results were analyzed with Kaplan-Meier curve and Cox regression.

Results: There were 44.8% of the tumors shrank. Median tumor local control interval was 10 months(15 months for AA and 9 months for GBM). Tumor local control probability was 37.9% for 1 year and 10.3% for 2 years. Median survival was 22.5 months for AA and 13 months for GBM and 15 months for all patients. The survival probability was 79.3% at 1 year and 20.6% at 2 years. Isocenter numbers and tumor volume were the prognostic factors for tumor control, but conformity index was prognostic factor for survival as determined by Cox regression analysis. Considered of pathology, only isocenter number and target volume significantly affected the tumor control interval. Complication appeared in 44.8% of the patients and the median interval of complication onset was 8 months. Symptomatic cerebral edema was observed in 31.0% of the patients.

Conclusion: Linac radiosurgery can effectively improve tumor local control and elongate survival for the patients with deep situated malignant gliomas. Tumor volume is the prognostic factor for tumor control, while conformity index is prognostic factor for survival.