The effectiveness, role and significance of Gamma Knife radiosurgery for ependymoma

Keywords: ependymoma, glioma, gamma knife, radiosurgery, outcome

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     Ependymoma is kown as a tumor which has relatively clear margin, and then basic therapeutic strategy is operative removal as much as possible. But it is often difficult to remove totally because of its growing region, and this tumor is often disseminated widely. So adjuvant therapy is mandatory. There have been no established chemotherapies and radiation therapy is common as adjuvant therapy at present, but it is difficult to control the tumor only by irradiation in many cases. Under these circumstances, we have used less invasive Gamma Knife surgery(GKS) for the patients of ependymoma. 
     Here we summarized the results of our cases and evaluated the effectiveness, role and significance of GKS for residual of operation, recurrence or dissemination of ependymoma.
     From June 1999 to July 2010, 112 lesions of 15 patients harboring around ependymoma were treated 31 times with GKS at our institution.
      All of the cases could be followed for a minimum of 8 months and were retrospectively examined. All of them had undergone operation, and conventional radiation therapy had also performed in 7cases. The cases consisted of 8 males and 7 females with a mean age of 36.5years(range; 6-74). And 7cases were Grade II and 8cases were Grade III.
     In these cases, the tumor volumes were 0.2-11.3cm3 and the tumors were irradiated 10-22Gy at the margin. Although 8cases were received repeated GKS 16times, retreatments for uncontrollable primary lesion were only 2times in 2cases. The others were all for newly disseminated lesions. The median follow up period after GKS was 49months, the control rate of primary lesions was 73.3% and that of disseminated lesions was 91.8%. And no definite side effect had been identified until now.
     This was a retrospective analysis.
     Though surgical removal is principle in the treatment of ependymoma, GKS is extremely effective as adjuvant therapy not only for the residual of operation, but also for the recurrence or dissemination. And it is also safe and useful for improvement of the prognosis and QOL. 
     So, under the careful consideration of case selection including the meaning of treatments, GKS should be more positively considered as one of the treatment strategy against ependymoma.


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