Audiologic and treatment outcomes after linear accelerator-based stereotactic irradiation for acoustic neuroma

Although surgical excision is the traditional treatment modality for acoustic neuroma, radiotherapy (RT) is gaining momentum as an alternative. This is particularly evident in patients with useful hearing, in whom fractionated RT offers the potential for hearing preservation. Our objective was to determine the disease control, hearing preservation (via audiograms), and toxicity rates after linear accelerator-based stereotactic radiation for acoustic neuroma.

A total of 72 acoustic neuroma patients underwent stereotactic irradiation and had at least 6 months of follow-up between October 1997 and March 2002. Of these, 45 received single-fraction stereotactic radiosurgery (SRS) and 27 received fractionated stereotactic radiotherapy (SRT). Before treatment, all SRS patients were functionally deaf and 23 of 25 SRT patients had useful hearing in the affected ear. The minimal peripheral dose was 12 Gy and 45 Gy in all SRS and SRT patients, respectively. Tumor control, toxicity, and hearing preservation were recorded.

The median follow-up in the SRS and SRT groups was 27 and 26 months, respectively. No tumor progression was seen after SRS and SRT. On the basis of the audiogram criteria, the 1-year and 2-year hearing preservation rate was 85% and 57%, respectively. The mean pre- and post-SRT speech recognition threshold was 20 and 38 dB, respectively. The mean proportion of pre- and post-SRT speech discrimination was 91% and 59%, respectively.

Stereotactic RT achieves good local control, with acceptable toxicity. RT fractionation appears to provide encouraging rates of hearing preservation.