Multisession stereotactic radiosurgery for large benign brain tumors of >3cm- early clinical outcomes

Abstract

Objective: To evaluate the clinical outcome of linear accelerator based multisession stereotactic radiosurgery (SRS) for large benign brain tumors of >3cm.

Methods: Between June 2009 and May 2011, 35 patients having large benign brain tumors of >3cm (≥15 cm³) were treated by multisession stereotactic radiosurgery. This retrospective study was carried out at Neurospinal & Medical Institute Karachi. There were 17 (48.6 %) males and 18(51.4 %) females. Median age was 36 years (range: 13-65 years). Median target volume was 49.4 cm³ (range: 15-184 cm³). The median marginal dose was 25 Gy (range: 20-27.5Gy) prescribed to a median 75% isodose line (range: 65-100 %). Median number of 5 fractions were used ranging 3-5 fractions.

Results: All the patients tolerated treatment very well. 21 (58.3%) patients had remarkable clinical improvement of neurological symptoms, 14 (38.9%) patients had stable symptoms, and only one patient had transient worsening of symptoms. No permanent neurological damage or radiation injury was seen. Radiologically, 9 (25.7%) patients achieved reduction in size of the tumor, 26(74.3 %) patients were having stable disease, and overall control rate was found to be 100 %. Median follow-up time from the end of SRS was 6.4 months (range: 1-22.5months).

Conclusion: Linear accelerator based multisession stereotactic radiosurgery for large benign brain tumors of >3cm is effective and well tolerated.

Keywords: Stereotactic radiosurgery (SRS); benign brain tumors; brain tumors; linear accelerator; multi session SRS; radiation injury.

Figure 1

Treatment setup for a case of young female with CP angle meningioma treated on synergy-S.

Figure 2

Beams Eye view, 7- beams treatment planning targeting on red colored GTV.

Figure 3

Various Structures drawn. In blue color body marked, red colored GTV, brain stem in light blue color, optic chiasma in purple color, yellow colored round eyes. While 7- beams direction shown out side the body.

Figure 4

CT scan slices showing CP angle meningioma in red lining, while compressed brain stem in light blue color.

Figure 5

CT slices showing wel conformed treatment plan. 75% prescription isodose line superimposing outer border of GTV with minimal fall off on adjacent normal structures.

Figure 6

(A) Gadolinium enhanced T1 weighted MRI brain, sagittal view of 40 years old lady having huge left cerebellopontine angle residual meningioma with grade III brain stem compression after initial surgery. Its size was about 60.8 mm x 41.4mm at the time of multisession SRS. (B)-Gadolinium enhanced T1 weighted MRI brain, sagittal view of left cerebellopontine angle meningioma, that has reduced to 47.3 mm x 30.5 mm at 9 months follow-up after multisession SRS without any signs of radiation injury. The patient had remarkable symptomatic (power, speech, imbalance and visual problems) improvement.

Figure 7

Gadolinium enhanced T1 weighted MRI brain, axial view in a 28 years old lady, showing a huge residual growth hormone secreting pituitary adenoma 46.2x28.7mm at the time of multisession stereotactic radiosurgery, optic chiasm was not identified. (B)-Gadolinium enhanced T1 weighted MRI brain, axial view showing remarkable shrinkage of tumor, optic chiasm was visible, only small residual thickening 6.7mm x 27.4mm on the left side at 15 months follow-up after multisession SRS, she had excellent clinical(headache, visual )improvement. Growth hormone level was dropped to 518 ng/ml from 1825 ng/ml of pre SRS levels at 3 months follow-up.