The aim of this paper was to determine prognostic factors for adult medulloblastoma treated with boost Gamma Knife surgery (GKS) following resection and craniospinal irradiation.
The authors performed a retrospective analysis of 12 adult patients with histologically proven medulloblastoma or supratentorial primitive neuroectodermal tumor who between February 1991 and December 2004 underwent ≥ 1 sessions of GKS for posttreatment residual or recurrent tumors (6 tumors in each group). Before GKS, all patients had undergone a maximal feasible resection followed by craniospinal irradiation. Nine patients also received systemic chemotherapy. Stereotactic radiosurgery was applied to residual and recurrent posterior fossa tumor as well as to foci of intracranial medulloblastoma metastases. The median time interval from initial diagnosis and resection to the first GKS treatment was 24 months (range 2–37 months). The mean GKS-treated tumor volume was 9.4 cm3 (range 0.5–39 cm3).
Following adjunctive radiosurgery, 5 patients had no evidence of tumor on magnetic resonance (MR) imaging, 3 patients had stable tumor burden on MR imaging, and 4 patients had evidence of tumor progression locally with or without intracranial metastases. All patients with tumor progression died. Eight patients survive with a mean cumulative follow-up of 72.4 months (range 21– 152 months). No acute radiation toxicity or delayed radiation necrosis was observed among any of the 12 patients. The majority of patients who achieved tumor eradication (80%) and tumor stabilization (67%) after GKS had residual tumor as the reason for their referral for GKS. The best outcomes were attained in patients with residual disease who were younger, had smaller tumor volumes, had no evidence of metastatic disease, and had received higher cumulative GKS doses.
Single or multiple GKS sessions were a well-tolerated, feasible, and effective adjunctive treatment for posterior fossa residual or recurrent medulloblastoma as well as intracranial metastatic medulloblastoma in adult patients.