Medical Center, Scranton, PA, 6Cleveland Clinic Foundation, Cleveland, OH ... Ottawa, ON, Canada, 3National University Cancer Institute (Singapore),.
E74
International Journal of Radiation Oncology Biology Physics
Results: There were 6 patients treated with 12-14 Gy in a single-fraction SRS and 27 patients with 18-21 Gy in 3-fraction SRS. The median age was 52 years (range, 21-70 years) and the ratio of male and female was 16/17. The median maximal diameter of skull base schwannoma was 2.29 cm (range, 0.9-4.43 cm). The median tumor volume was 4.73 cm3 (range, 0.47-23.9 cm3). The median biological equivalent dose (BED2) was 94.5 Gy (range, 72-112 Gy) if a/b was equal to 2. With the median follow-up of 26.6 months (range, 14.4-46.1 months), the rate of local tumor control was 100%. Compared with that of pre-SRS, the median maximal diameter of skull base schwannoma significantly decreased (2.29 cm vs 1.45 cm, P Z 0.001). The Patients treated with singlefraction and fractionated SRS were 18.2% (6/33) and 81.8% (27/33), respectively. Compared with single SRS, the fractionated SRS significantly decreased BED2 (97.5 Gy vs 94.5 Gy, P Z 0.015) and had relative large volume of planning target volumes (PTV) (3.29 cm3 vs 5.46 cm3, P Z 0.37). There was no statistical difference in local tumor control between single and fractionated SRS. The cranial nerve symptoms were stable and improved after SRS, including tinnitus (80%, 12/15), hearing loss (91%, 20/22), trigeminal paresthesia (62%, 8/13) and trigeminal neuralgia (100%, 2/2). The side effects After SRS involved hemifacial spasm (18%, 6/33), facial nerve paralysis (6%, 2/33), cerebella dystaxia (6%, 2/33) and encephaledema (15%, 5/33), but most symptoms were transient and mild. There was no significant statistically differences in tinnitus, hearing loss, trigeminal paresthesia and neuralgia between single and fractionated SRS. Conclusion: The fractionated SRS was an effective dose-fraction model for skull base schwannoma, offering a similar effect to single SRS and a promising outcome in reducing risk of cranial nerve complication. Author Disclosure: J. Wang: None. L. Pan: None. Z. Ju: None. B. Qu: None. W. Wang: None. L. Sun: None. X. Yu: None. Z. Lin: None.
Gy, and for 2410 (79%) tumors 24 Gy. The mean isodose line was 60% 12%, and the mean conformality index was 2.21 1.31. 87 patients (10%) had LP of 104 tumors (3%) and 148 patients (17%) had RN of 199 tumors (7%). SRN was seen in 104 tumors (3%) and 81 patients (9%). On multivariable analysis, tumor diameter (>1 versus < 1 cm, SHR 2.32, P