Prognostic factors for tumor recurrence after gamma knife radiosurgery of partially resected and recurrent craniopharyngiomas

A study was conducted to clarify the prognostic factors related to recurrence of craniopharyngioma and to improve the quality of life of patients by the treatment with intentional partial removal and gamma knife radiosurgery. One hundred cases of craniopharyngioma have been treated at Komaki City Hospital since 1991. In a mean follow-up period of 65.5 months, the tumor control rate was 79.5%. The 5-and 10-year actuarial survival rates were 94.1% and 91%, respectively. However, the recurrence-free survival rates were 73.6% at 5 years and 60.2% at 10 years. Nine factors thought to be related to the recurrence were selected from past references and previous studies, including gender, age, pediatric (=17 years) or adult patient, partial removal or recurrence, mean tumor diameter, tumor type (solid or cyst), pathological types (squamous cell or adamantinoma), number of previous treatments, and radiation dose. Statistical analysis was performed to determine which factors had a significant prognostic impact. Multivariate analysis showed that mean tumor diameter and radiation dose were independent predictors of outcome. To maximize the prognostic power of these factors, cut-offlevels were determined using ROC analysis. These levels were 19 mm for tumor diameter and 13.2 Gy for marginal dose. Significant prognostic factors related to recurrence of craniopharyngioma are tumor diameter and radiation dose. A tumor diameter of <19 mm and a marginal dose of =13.2 Gy are favorable prognostic factors for gamma knife radiosurgery.