Lower radiation dose safer, still effective for acoustic neuromas
NEW YORK (Reuters Health), Jan 19 - Treating acoustic neuromas with fractionated stereotactic radiotherapy (FSR) at a radiation dose 10% lower than commonly used for this purpose better preserved patients’ hearing, while still achieving a 100% local tumor control rate, in a study published online by the International Journal of Radiation Oncology, Biology, Physics
“This is a potentially practice-changing finding,” Dr. David W. Andrews of Jefferson Medical College, Thomas Jefferson University, Philadelphia, said in a prepared statement that accompanied the report. “We are now working to design a study to directly compare FSR with other treatment options, including stereotactic single fraction radiosurgery.”
The researchers reviewed data on 89 patients newly diagnosed with acoustic neuroma for whom serial audiometric data were available. Before treatment, 61 patients had Gardner-Robertson class 1 hearing, and 28 had class 2 hearing.
All patients were treated with 1.8-Gy isosurface fractions delivered daily for five days/week for four to six weeks. The 43 patients treated prior to 2002 received a cumulative dose of 50.5 Gy, while the 46 treated after November 2002 received a total dose of 46.8 Gy. The dose reduction was based on published research into stereotactic single-fraction radiosurgery (SRS), in which a decrease in the dose led to reduced morbidity with continued tumor control.
Post-FSR, the pure tone average in the lower-dose cohort was significantly improved compared with the higher-dose cohort (33 dB versus 40 dB, p = 0.023). In addition, at a three-year follow-up, the raw hearing preservation rate was better in the lower-dose group (79% versus 68% in the higher-dose group), and the actuarial hearing preservation rate was significantly longer for the lower-dose group (165 versus 79 weeks, p = 0.0318).
On multivariate analysis, only dose cohort and pretreatment Gardner-Robertson grade contributed significantly to the likelihood of hearing preservation.
The researchers say it remains to be seen whether an additional dose reduction might provide an even better outcome, as well as how FSR would compare with SRS, given optimal doses on both.
Int J Radiation Oncology Biol Phys 2008.
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