Lower radiation dose saves hearing in acoustic neuromas

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NEW YORK (Reuters Health), Nov 7 - Hearing can be preserved in patients with acoustic schwannomas and "serviceable" hearing by delivering lower doses of fractionated stereotactic radiotherapy, which allows the radiation to conform to the shape of the tumor around the nerve.

A lower dose can be given without an adverse effect on survival, investigators at Thomas Jefferson University in Philadelphia announced here during the 48th annual meeting of the American Society of Radiation Therapy and Oncology.

Dr. Maria Werner-Wasik presented her team's findings for 115 patients with acoustic schwannomas treated with either 50.4 Gy or 46.8 Gy stereotactic unfractionated radiotherapy.

Baseline and follow-up audiograms were conducted. Serviceable hearing was defined as a Pure Tone Average between 0-50 decibels and a Speech Discrimination Score above 50%. Median time at follow-up was 69 months for the high-dose group and 29 months for the low-dose group.

Local control was 98% in high-dose patients and 100% in low-dose patients after radiation therapy.

"This (lower) dose is very conformal," Dr. Werner-Wasik told Reuters Health in an interview during the meeting. "It's the same dose used for a benign or basal tumor...Quality of life is better because hearing is preserved."

In the high-dose group at baseline, serviceable hearing averaged 69% and measurable hearing at 31% in the high-dose group. Initial Pure Tone Average was 32.5 decibels and was 47 decibels at follow-up. The initial Speech Discrimination Score was 86% and at follow-up it was 64%.

In the low-dose group, baseline serviceable and measurable hearing was 84% and 13%, respectively. Initial Pure Tone average was 23 decibels and 40 decibels at follow-up. Initial Speech Discrimination Score was 80% and at follow-up, 70%.

The change between baseline and follow-up Pure Tone Average and Speech Discrimination Score were not statistically significantly different between low- and high-dose groups, overall. However, when the two cohorts were matched according to baseline Pure Tone Average, there was less hearing loss in patients receiving the lower dose of radiation.

"The lower dose gives essentially the same local control," Dr. Werner-Wasik pointed out, adding that the approach may be useful for tumors surrounding other vital structures. She noted that another benefit of the low-dose approach is that it requires fewer treatments and shorter treatment times.

By Martha Kerr

Last Updated: 2006-11-07 16:11:19 -0400 (Reuters Health)

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