Fractionated proton beam radiotherapy for acoustic neuroma.
OBJECTIVE
This study evaluated proton beam irradiation in patients with acoustic neuroma. The aim was to provide maximal local tumor control while minimizing complications such as cranial nerve injuries.


METHODS
Thirty-one acoustic neuromas in 30 patients were treated with proton beam therapy from March 1991 to June 1999. The mean tumor volume was 4.3 cm(3). All patients underwent pretreatment neurological evaluation, contrast enhanced magnetic resonance imaging, and audiometric evaluation. Standard fractionated proton radiotherapy was used at daily doses of 1.8 to 2.0 cobalt Gray equivalent: patients with useful hearing before treatment (Gardner-Robertson Grade I or II) received 54.0 cobalt Gray equivalent in 30 fractions; patients without useful hearing received 60.0 cobalt Gray equivalent in 30 to 33 fractions.


RESULTS
Twenty-nine of 30 patients were assessable for tumor control and cranial nerve injury. Follow-up ranged from 7 to 98 months (mean, 34 mo), during which no patients demonstrated disease progression on magnetic resonance imaging scans. Eleven patients demonstrated radiographic regression. Of the 13 patients with pretreatment Gardner-Robertson Grade I or II hearing, 4 (31%) maintained useful hearing. No transient or permanent treatment-related trigeminal or facial nerve dysfunction was observed.


CONCLUSIONS
Fractionated proton beam therapy provided excellent local control of acoustic neuromas when treatment was administered in moderate doses. No injuries to the Vth or VIIth cranial nerves were observed. A reduction in the tumor dose is being evaluated to increase the hearing preservation rate.
Bush
David A
DA
Department of Radiation Medicine, Loma Linda University Medical Center, Loma Linda, California 92354, USA. dbush@dominion.llumc.edu
McAllister
Calvin J
CJ
Loredo
Lilia N
LN
Johnson
Walter D
WD
Slater
James M
JM
Slater
Jerry D
JD
D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D001301:Audiometry, Pure-Tone; D003037:Cobalt Radioisotopes / Q000627:therapeutic use*; D016371:Cranial Irradiation; D019583:Dose Fractionation, Radiation; D005154:Facial Nerve / Q000528:radiation effects; D005260:Female; D005500:Follow-Up Studies; D006801:Humans; D008297:Male; D008875:Middle Aged; D009464:Neuroma, Acoustic / Q000000981:diagnostic imaging / Q000532:radiotherapy*; D011867:Radioisotope Teletherapy; D011880:Radiotherapy Planning, Computer-Assisted; D014057:Tomography, X-Ray Computed; D016896:Treatment Outcome; D014276:Trigeminal Nerve / Q000528:radiation effects; D000159:Vestibulocochlear Nerve / Q000000981:diagnostic imaging
D003037:Cobalt Radioisotopes