To frame or not to frame? Cone-beam CT-based analysis of head immobilization devices specific to linac-based stereotactic radiosurgery and radiotherapy.

PURPOSE: Noninvasive frameless systems are increasingly being utilized for head immobilization in stereotactic radiosurgery (SRS). Knowing the head positioning reproducibility of frameless systems and their respective ability to limit intrafractional head motion is important in order to safely perform SRS. The purpose of this study was to evaluate and compare the intrafractional head motion of an invasive frame and a series of frameless systems for single fraction SRS and fractionated/hypofractionated stereotactic radiotherapy (FSRT/HF-SRT). METHODS: The noninvasive PinPoint system was used on 15 HF-SRT and 21 SRS patients. Intrafractional motion for these patients was compared to 15 SRS patients immobilized with Cosman-Roberts-Wells (CRW) frame, and a FSRT population that respectively included 23, 32, and 15 patients immobilized using Gill-Thomas-Cosman (GTC) frame, Uniframe, and Orfit. All HF-SRT and FSRT patients were treated using intensity-modulated radiation therapy on a linear accelerator equipped with cone-beam CT (CBCT) and a robotic couch. SRS patients were treated using gantry-mounted stereotactic cones. The CBCT image-guidance protocol included initial setup, pretreatment and post-treatment verification images. The residual error determined from the post-treatment CBCT was used as a surrogate for intrafractional head motion during treatment. RESULTS: The mean intrafractional motion over all fractions with PinPoint was 0.62 ± 0.33 mm and 0.45 ± 0.33 mm, respectively, for the HF-SRT and SRS cohort of patients (P-value = 0.266). For CRW, GTC, Orfit, and Uniframe, the mean intrafractional motions were 0.30 ± 0.21 mm, 0.54 ± 0.76 mm, 0.73 ± 0.49 mm, and 0.76 ± 0.51 mm, respectively. For CRW, PinPoint, GTC, Orfit, and Uniframe, intrafractional motion exceeded 1.5 mm in 0%, 0%, 5%, 6%, and 8% of all fractions treated, respectively. CONCLUSIONS: The noninvasive PinPoint system and the invasive CRW frame stringently limit cranial intrafractional motion, while the latter provides superior immobilization. Based on the results of this study, our clinical practice for malignant tumors has evolved to apply an invasive CRW frame only for metastases in eloquent locations to minimize normal tissue exposure.

Fractionated stereotactic radiotherapy for the treatment of vestibular schwannomas: combined experience of the Toronto-Sunnybrook Regional Cancer Centre and the Princess Margaret Hospital.

PURPOSE: To evaluate the efficacy and toxicity of fractionated stereotactic radiotherapy (FSRT) for vestibular schwannomas in patients treated at two university-affiliated hospitals. METHODS AND MATERIALS: Thirty-nine patients were treated between April 1996 and September 2000. The median age was 56 years (range: 29-80), and median maximal tumor diameter was 20 mm (range: 9-40). A total of 11 patients had fifth and/or seventh cranial nerve dysfunction before irradiation; 2 patients had only facial weakness, 5 patients had only facial numbness, and 4 patients had both facial weakness and numbness. Thirty-three patients were treated with primary FSRT, and 6 patients were treated for recurrent or persistent disease after previous surgery. All patients were treated with 6-MV photons using a stereotactic system with a relocatable frame. The 39 patients received 50 Gy in 25 fractions over 5 weeks. Median follow-up was 21.8 months (range: 4.4-49.6). RESULTS: Local control was achieved in 37 patients (95%). Two patients experienced deterioration of their symptoms at 3 and 20 months as a result of clinical progression in one case and tumor progression in the other and underwent surgery post FSRT. A total of 19/28 (67.9%) patients preserved serviceable hearing after FSRT. Deterioration of the facial and trigeminal nerves was observed in only 2 patients who were treated with surgery post FSRT. CONCLUSION: FSRT provided excellent tumor control with minimal morbidity and good hearing preservation in this cohort of patients. Longer follow-up is required to confirm long-term control rates.

Capillary hemangioma of the cavernous sinus. Report of two cases.

Capillary hemangiomas are rare benign vascular tumors that tend to occur in children. Whereas the majority of hemangiomas may regress spontaneously, those associated with functional sequelae or severe symptoms may require treatment. Two patients with capillary hemangiomas of the cavernous sinus that caused neurological symptoms were treated with fractionated stereotactic radiation therapy. Both hemangiomas had shown a progressive increase in size during observation before radiation therapy; both tumors regressed after radiotherapy. Up to the time of the last follow-up evaluation both patients experienced symptomatic relief after radiation. One patient's tumor remains in complete remission and the second tumor continues to demonstrate minor residual contrast enhancement without progression. The authors conclude that fractionated stereotactic radiation therapy is a useful treatment modality in the management of symptomatic capillary hemangiomas when these tumors arise in regions of the brain or skull base in which a complete resection cannot be accomplished.