Combination of surgical resection and interstitial radiosurgery as a treatment concept for WHO grade II glioma in complex localisation

Objective: The current prospectively designed pilot study analyzed the feasibility and outcome of a combined microsurgical / interstitial radiosurgical approach for patients with highly eloquently located supratentorial WHO Grade II glioma.

Methods: Between 1998 and 2005 36 patients fulfilled the study protocol: Tumor resection was performed as radically as possible in every patient using multimodal intraoperative stimulation techniques; Interstitial radiosurgery (IRS) was done in remaining or recurrent circumscribed tumors with a diameter <3,5cm. IRS of de-novo tumors was performed three months after resection. The reference dose (calculated to the boundary of the tumor) was 55 Gy and the dose rate was 10 cGy/h (median). The median duration of irradiation was 26 days. Reference point for estimation of treatment effects was the date of IRS. Last follow-up was performed at March 2005. Treatment response after IRS was classified according to the Macdonald criteria (Macdonald et al., J Clin Oncol 1990 Jul; 8(7): 1277–80); Time to tumor progression and malignant transformation was estimated with the Kaplan Meier method. Any adverse sequel potentially attributable to treatment was considered as morbidity.

Results: IRS was performed in 21 patients after partial tumor resection and in 15 patients with recurrent tumors. Median follow-up was 64 months. 5-year progression free survival was 62% and the 5-year malignant transformation rate was 19%. Complete remission, partial remission and tumor control after IRS was seen in 9, 10, and 17 patients respectively. The median KPS at the time of the last follow-up was unchanged as compared to the pretreatment score. Microsurgical related transient and permanent morbidity was 47% and 10%, respectively. Transient (permanent) morbidity after IRS was 6% (0%). There was no mortality in this series.

Conclusion: IRS in combination with microsurgery is a feasible treatment concept for highly eloquently located glioma. Whereas transient morbidity after open tumor resection of complex located glioma still remains high IRS is safe and minimally invasive and offers the possibility to withhold external beam radiation.