P09.19.B STEREOATACTIC RADIOTHERAPY IN SKULL BASE PARAGANGLIOMAS-THE NATIONAL RESEARCH INSTITUTE OFONCOLOGY, GLIWICE BRANCH EXPERIENCE.

Abstract BACKGROUND Paragangliomas of the skull base are benign tumors but can locally infiltrate and destroy surrounding anatomic structures, resulting in neurologic symptoms, which depend on the size and location. Consensus guidelines on the management of these tumors are lacking, however treatment options for paragangliomas consist of surgical resection and radiation therapy, including stereotactic and fractionated radiotherapy. Stereotactic radiotherapy is performed in shorter overall treatment times with the potential for better local tumor control. AIM We retrospectively evaluated the efficacy of stereotactic radiotherapy with Cyber Knife, in patients with skull base paragangliomas, treated in National Center of Oncology in Gliwice between 2010-2020. MATERIAL END METHODS We evaluated 24 patients diagnosed with skull base paragangliomas with median age of 51,6 y (range 15,5-70 y). There were 19 women and 5 men. Primary localization of tumor was: internal jugular vein region in 18pts and temporal bone pyramid in 6 pts. Medial diameter of tumor assessed by MRI was 28,5mm (range 13- 55 mm). Eleven patients were offered neurosurgical procedures as primary treatment: partial resection in 4 pts, embolisation in 5 pts and combined in 2 pts. Mean time since surgical treatment to referral to radiotherapy was 2,3 y. All patients received stereotactic Cyber Knife radiotherapy with median dose of 20 Gy/g (range 15-30 Gy/g). All but two patients received three factions of radiotherapy. One patient received single fraction of 15 Gy/g and the other 6 fractions of 5 Gy/g. Median follow-up was 7,18 y (range, 0,55-13,1 y). Treatment response was evaluated in MRI with partial regression in 4 patients, stabilization of tumor in 15 pts. While follow-up, five patients progressed with median time to progression of 6,4 y (range 4,9-9,49 y). Four patients received the second course of Cyber Knife stereotactic radiotherapy with 18 Gy/g in 3 fractions with stable disease in MRI while follow up. One patient is while treatment planning for re-irradiation. Radiotherapy was well tolerated. CONCLUSIONS Stereotactic Cyber Knife radiotherapy is an effective treatment of skull base paragangliomas and should be considered both as primary management and as adjuvant strategy for residual tumors after initial resection and/or embolisation.