Does Early Radiosurgery To Residual Enhancement Improve Outcome Following Subtotal Resection Of Gbm?

Mirhadi Amin1, Keith Black1, Jeremy Rudnick1, Ray Chu1, John Yu1, Surasak Phuphanich1, Behrooz Hakimian.1

1Cedars Sinai Medical Center, Los Angeles, USA

Keywords: gamma knife, outcome, glioblastoma multiforme, radiosurgery, brain tumor

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     Standard of care for post-op management of GBM is external beam RT concurrent with chemotherapy. Based upon prospective and retrospective studies, the role of radiosurgery is limited. However, previous studies have assessed its role either for recurrence or to the entire resection cavity as a boost. Local failure is common after combined fractionated external beam and radiosurgery, but it is known that degree of resection is associated with survival in GBM.
     In this analysis, we therefore sought to evaluate the role of adding radiosurgery to the residual portion of tumor following subtotal resection or biopsy in conjunction with standard therapy to help maximize local control and survival.
     We performed a single institution, retrospective analysis of 13 consecutive patients who underwent subtotal resection, external beam RT, and temozolomide in conjunction with radiosurgery (using the Leksell Gamma Knife).
     Radiosurgery was delivered either before the start of standard therapy or within 6 months of completion. The radiosurgery target was to residual contrast enhancement only. The patients were treated from 11/06 to 1/09. Average dose to the tumor bed was 14 Gy (range 12-18). The study population consisted of 9 males and 4 females. Age range was 53-79. KPS ranged from 60-100.
     All patients in this analysis were determined to be RPA class 4 (Lamborn KR, Neuro-Oncology 2004). 8 out of 13 patients were alive at the time of analysis. Median follow-up time was 47.2 weeks. The median overall survival time for the patients in this study was 74.9 weeks (95% CI: 59.4 ,inf). Progression was defined using Macdonald criteria and occurred in 4 patients resulting in 3 deaths. 2 patients died without progression; 1 from infection and another from pulmonary embolism. Of the 4 progressors, 1 had progression at the site of radiosurgery, the other 3 within the standard RT volume. The median progression free survival for the entire cohort was 60 weeks (95% CI: 45.1,inf).
     This is a retrospective study.
     Radiosurgery is a safe and effective tool for delivering high doses of radiation to small volumes. Previous studies have attempted to treat high volume GBM with limited benefit and a potential benefit to small volume, sub-totally resected GBM patients may have been obscured.
     Historically, median survival for RPA class 4 patients is 35 weeks. In this analysis of RPA class 4 patients, median survival is 74.9 weeks. For GBM, maximal safe resection should be performed. If image-complete removal cannot be accomplished, then radiosurgery to the site of gross residual may improve outcome. Longer follow up and a randomized trial are needed to determine whether or not the impact of radiosurgery is meaningful in this setting.


Project Roles:

M. Amin (), K. Black (), J. Rudnick (), R. Chu (), J. Yu (), S. Phuphanich (), B. Hakimian. ()