Long-term Results of Gamma Knife Radiosurgery for Craniopharyngioma

두개인두종의 감마나이프 치료 후 장기 추적 결과

Objectives : The optimal treatment of craniopharyngioma is controversial. Despite recent advances in microsurgical management, complete surgical removal of craniopharyngioma remains very difficult. Radiation added to surgery is effective, but radiation therapy resulted in untoward side effect in young patient. Gamma knife radiosurgery offers the theoretical advantage of a reduced radiation dose to surrounding structures during the treatment of residual or recurrent craniopharyngioma compared with fractionated radiotheraphy. We described retrospective analysis of tumor size and clinical symptoms of patients after gamma knife radiosurgery in residual or recurrent craniopharyngioma were performed. Material and Methods : From September 1990 to January 2000, 18 patients of craniopharyngioma were treated by gamma knife radiosurgery. All patient had undergone surgery, but residual or recurrent tumor was found and all of them treated postoperative gamma knife radiosurgery. The mean age was 19(from 6 to 66) and male to female ratio was 10 to 8 and 8 patients were below 15 years old. In young age group(below age 15), the average volume of the tumor was $2904.8mm^3$ and mean maximal gamma knife dose was 34.9Gy. In old age group(older than 15), the average volume of the tumor was $2590.4mm^3$ and mean maximal gamma knife dose was 45.2Gy. The size of the tumor was average $2730.1mm^3$($88-12000mm^3$), mean average radiation dose was 40.7Gy and the mean prescription dose was 17.6 Gy(4-35Gy) delivered to a median prescription 50.7% isodose. Results : The follow up was from 1 year to 9 years(mean 59.1 months) after gamma knife radiosurgery. The tumor was controlled in 13(72.2%) patients. The tumor decreased in 9 patients and not changed in 4 patients. The tumor size increased in 4(22.2%) patients during follow up period. In two cases the tumor size increased because of its cystic portion was increased, but their solid portion of the tumor was not changed. In another two patients, the solid portion of the tumor was increased. So, one patient underwent reoperation and the other patient underwent operation and repeated gamma knife radiosurgery. The tumor recurred in one case(5.6%) that is a outside of irradiated site. The presenting symptoms were improved in 4 patients(improved visual acuity in 1, controlled increased intracranial presure sign in 3 patients). In one case, visual acuity decreased after gamma knife radiosurgery. The endocrine symptoms were not influenced by gamma knife radiosurgery. Conclusion : Craniopharyngioma can be treated successfully by gamma knife radiosurgery. Causes of the tumor regrowth are inadequate dose planning because of postoperatively poor margination of the tumor, close approximation of optic nerve and residual tumors outside the target lesion. Recurrence can develop 4 years after gamma knife radiosurgery. Volume is important, but the accurate targeting is more important to prevent tumor recurrence. If the tumor definition is not clear during planning gamma knife surgery, long-term image follow up is required.