Stereotactic radiosurgery and fractionated stereotactic radiotherapy for the treatment of acoustic schwannomas: Comparative observations of 125 patients treated at one institution

Background: Stereotactic radiosurgery (SRS) and, more recently, fractionate d stereotactic radiotherapy (SRT) have been recognized as noninvasive alter natives to surgery for the treatment of acoustic schwannomas. We review our experience of acoustic tumor treatments at one institution using a gamma k nife for SRS and the first commercial world installation of a dedicated lin ac for SRT. Methods: Patients mere treated with SRS on the gamma knife or SRT on the li nac from October 1994 through August 2000. Gamma knife technique involved a fixed-frame multiple shot/high conformality single treatment, whereas lina c technique involved daily conventional fraction treatments involving a rel ocatable frame, fewer isocenters, and high conformality established by nonc oplanar arc bean shaping and differential beam weighting. Results: Sixty-nine patients were treated on the gamma knife, and 56 patien ts were treated on the linac, with 1 NF-2 patient common to both units. Thr ee patients were lost to follow-up, and in the remaining 122 patients, mean follow-up was 119 +/- 67 weeks For SRS patients and 115 +/- 96 weeks for S RT patients. Tumor control rates were high (greater than or equal to 97%) f or sporadic tumors in both groups but lower for NF-2 tumors in the SRT grou p. Cranial nerve morbidities were comparably low in both groups, with the e xception of functional hearing preservation, which was 2.5-fold higher in p atients who received conventional fraction SRT. Conclusion: SRS and SRT represent comparable noninvasive treatments for aco ustic schwannomas in both sporadic and NF-2 patient groups. At 1-year follo w-up, a significantly higher rate of serviceable hearing preservation was a chieved in SRT sporadic tumor patients and may therefore be preferable to a lternatives including surgery, SRS, or possibly observation in patients wit h serviceable bearing. (C) 2001 Elsevier Science Inc.