Stereotactic radiosurgery of intracranial tumors: a comparison of intensity-modulated radiosurgery and dynamic conformational arc.

PURPOSE: Intensity-modulated radiosurgery (IMRT) and dynamic conformational arc (DCA) are two techniques for linac-stereotactic radiosurgery using the micro-multileaf collimator. The objective of this study is to examine advantages and disadvantages of these techniques in the treatment of treatment of intracranial tumors. MATERIALS AND METHODS: SRS treatment plans were developed for 21 patients with vestibular schwannoma, glomus jugulare, pituitary adenoma and cavernous sinus meningioma. For all patients, we developed an IMRT and a DCA plan using BrainLab Iplan 4.1. Plans were evaluated using the target coverage conformity index (CI), homogeneity index (HI), Gradient Index (GI) and doses in critical structures (optic pathways and brainstem). RESULTS: In the overall comparison of both techniques, HI and CI was better in the IMRT group, showing a statistically significant difference. The GI was similar in two groups. Comparison of the mean dose in critical structures of the techniques revealed no statistically significant differences. The DCA plan was acceptable in 9 patients and IMRT in 15 patients. IMRT was preferred in 14 out of 15 patients due to better CI and lower dose in critical structures with adequate target coverage. CONCLUSIONS: IMRT is the preferred stereotactic radiosurgery technique for most intracranial benign tumors close to critical structures.

Bilateral malignant metastases to the internal auditory canal: radiosurgical management.

Malignant melanomas constitute 1-8% of all malignant tumors and are the third most common tumor to metastasize to the central nervous system. However, metastases to the cerebellopontine angle (CPA) are rare, accounting for only 0.2 to 0.7% of the lesions identified in this location Case Report. A 62-year-old white man with a history of melanoma of the back, who had had all lesions completely excised, was reportedly tumor-free for 6 years. The patient presented bilateral metastatic CPA melanoma. Left side tumor was treated with surgery with partial resection (lost hearing) and radisorugery. Right side lesion was treated with radiosurgery and hearing preserved for 8 months, tumor controlled for 12 months, until death due to leptomeningeal carcinomatosis after 13 months of radiosurgey. The patient underwent intensity-modulated stereotactic radiosurgery using BrainLab Iplan 4.1 for both IAC lesions, the dose was 18Gy prescribed to the 80% isodose line delivered by 11 fields. The patient presented no post-radiosurgery neurological complications. Conclusion: In patients with lesions in the CPA, a diagnosis of melanoma should be included, particularly in cases with rapid progression of symptoms. Therefore, radiosurgery is a viable treatment option since the hearing can be preserved and tumor control achieved.