(P042) Toxicity and Treatment Outcomes in Single vs Multifractionated Radiotherapy for Acoustic Neuromas

Ajaykumar B. Patel, MD, Jennifer L. Peterson, MD, Colleen S. Thomas, MS, Michael G. Heckman, MS, Stephen J. Ko, MD, Katherine S. Tzou, MD, Robert C. Miller, MD, Laura A. Vallow, MD, Steven J. Buskirk, MD; Department of Radiation Oncology, Division of Medical Statistics and Informatics, Mayo Clinic Florida

PURPOSE: To review our institution’s experience in treating acoustic neuromas by comparing toxicity and treatment outcomes using stereotactic radiosurgery (SRS) vs fractionated stereotactic radiation therapy (FSRT).

MATERIALS AND METHODS: A total of 57 consecutive patients were treated with either single-fraction SRS (n = 26) or FSRT (n = 31) for acoustic neuroma at our institution between March 2000 and November 2013. Median dose was 1,200 cGy (range: 1,160–1,600 cGy) for SRS and 2,000 cGy (range: 2,000–2,500 cGy) for FSRT. Data were collected on treatment toxicities and progression in 22 SRS and 29 FSRT patients with sufficient follow-up data. Toxicities were graded by the Common Terminology Criteria for Adverse Events version 4.0 (CTCAE v4.0).

RESULTS: Median follow-up length was 39 months in SRS patients and 27 months in FSRT patients. Median maximum tumor dimension for SRS and FSRT was 1.4 cm and 1.6 cm, respectively (P = .097). The most common complication was grade 3 ipsilateral hearing loss, which was experienced in 23% of SRS patients and 35% of FSRT patients. Grade 2 vestibular disorder was experienced in 27% of SRS patients and 21% of FSRT patients. No patient experienced grade ≥ 3 vestibular disorder in either group. Grade 1 and 2 facial nerve toxicity occurred in 14% of SRS patients and 10% of FSRT patients. Grade 1 or 2 trigeminal nerve toxicity occurred in 23% of SRS patients and 10% of FSRT patients. No patient experienced grade ≥ 3 facial nerve or trigeminal nerve toxicity. Only three patients (one in FSRT, two in SRS) had disease progression. At 1, 3, and 5 years after the start of treatment, the cumulative incidence of progression was 0%, 8%, and 8% for SRS patients and 0%, 0%, and 11% for FSRT patients, respectively (P = .47). There was no statistically significant difference in likelihood of any individual type of complication or disease progression between patients treated with SRS or FSRT (all P >.12). There was no evidence of an association with occurrence of different types of complications for maximum tumor dimension, SRS dose, or FSRT dose (all P ≥ .19).

CONCLUSION: FSRT and SRS in treatment for acoustic neuromas had similar outcomes and toxicity at our institution. Both modalities appear to be successful at providing high tumor control with acceptable toxicities in the noninvasive treatment of acoustic neuromas.

Proceedings of the 97th Annual Meeting of the American Radium Society - americanradiumsociety.org