Analysis of the results of gamma knife radiosurgery for hemangioblastomas of the brain and the factors related to the tumor recurrence

Objective To assess the 5-year-result of leksell gamma knife (LGK) in controlling hemangioblastomas of the brain (HB) and to analyze the factors related to tumor recurrence or development of new tumors. Methods From November 1993 to September 2001,35 patients,28 males and 7 females,aged 36 (16～61),18 with multiple tumors and 17 with solitary tumor,the number of tumors being 93 in total,were treated by LGK. Twenty-one patients with HBs were associated with von Hippel-Lindau disease (VHLD). The tumor size ranged 5～55 mm with a mean size of 13 mm. The mean maximum irradiation dose was 35.6 Gy (20.0～50.0 Gy) at tumor center and the mean minimum dose was 17.2 Gy (12.0～24.0 Gy) at tumor periphery. Fisher exact test,independent T test and Wilcoxon rank sum W test were used to analyze the results of LGK on solitary and multiple HBs,the recurrent time of the HBs,and the relation between minimum irradiation dose and tumor control. Results 35 patients had been followed for 24-114 months with a mean value of 66 months. 29 patients were alive and 6 died. Of the 29 patients 21 achieved satisfying tumor control,and 8 patients underwent open surgery because of tumor-associated cysts enlarging or development of new tumors after LGK. 21 patients had improvement or remained stable in neurological status. Of the 8 reopened patients,2 had deteriorated symptoms and the other 6 remained neurologically stable. Of the 35 patients,7 developed new tumor during the follow-up period,and 5 had second LGK. Tumor control: Of the 29 cases,solitary or multiple tumors in 23 patients decreased in volume or remained the same,although two developed new tumors. The result of LGK in controlling HBs showed no significant difference between the solitary and multiple HBs ( P 0.05),but the dose of long-term tumor control was significantly higher than that of uncontrolled tumors ( W =98,P 0.01). The tumor control rate was 94% 1 year after; 85% 2 years after; 82% 3 years after; 79% 4 years after; and 71% 5 years after. For the patients with solitary tumor,the mean time of development of new tumor was 63 months,but for the patients with multiple HBs,the time was 25 months. There was a significant difference between the two groups ( t =3.987,P 0.001). With margin dose of 18 Gy,histopathology showed that no tumor cell was found and there were coagulation necrosis,hyaline degeneration and fibrosis tissues in the tumor nodule 48 months after LGK. Conclusion LGK is a good choice for small- or medium-sized,solid HB in long term,especially when tumor margin dose is 16-20 Gy. Although LGK can treat multiple tumors in one single treatment session,for HB in patients associated with VHLD,LGK faces the problem of tumor recurrence or development of new tumor.