Gamma Knife Radiosurgery for Craniopharyngioma

ABSTRACT

OBJECTIVE: The purpose of this study are to evaluate the effectiveness of Gamma Knife radiosurgery(GKS) as a treatment of craniopharyngioma and to investigate the proper dose planning technique in GKS for craniopharyngioma. METHOD: Between May 1992 and March 1999, seven Gamma Knife radiosurgical procedures were done for residual tumor mass of 6 patients with craniopharyngioma after microsurgical resection. Conventional radiation therapy was not performed. In this study, their clinical, radiological and radiosurgical data were analyzed and the radiation dosage to the optic pathway, hypothalamus, pituitary stalk, and cavernous sinus were calculated and correlation with clinical outcome was evaluated. The mean follow-up period was 33.5 months(12.3-55.2 months). RESULT: The mean tumor volume was 4.4cc(0.4-18.0cc) and the maximum radiation dose ranged from 14 to 32 Gy(mean 20.9Gy). The radiation was given with isodose curve, 50-90% and the marginal dose varied within 8-22.4Gy(mean 12.7Gy). The mean number of isocenter was 4.3(1-12). The tumor was well controlled in all cases. In 5 of 7 cases, the size of tumor decreased to 10-50% of pre-GKS volume and remaining two showed no volume change. The mean dose to optic pathway was 5.7Gy(5.1-11.2Gy) and there were no complications. CONCLUSION: GKS seems to be effective for control of craniopharyngioma as an adjuvant treatment after microsurgical resection and even suboptimal dose for tumor margin is considered to be enough for tumor control. It is safe with careful dose planning to protect surrounding important structures, especially optic pathway. We believe conventional radiation therapy should be avoided because it has limitation for dose planning of additional treatments such as radiosurgery or intracystic instillation of radioisotope in case of recurrence.