224 1. J. Radiation Oncology@Biology@Physics Volume 39, Number 2, Supplement, 1997

1017 ACOUSTIC NEUROMAS: SINGLE DOSE VS FRACTIONATED THERAPY

Fuss M.*, Debus I.*, Lohr F *, Engenhart-Cabillic R O, Wannenmacher M.*

* Dept of Radiation Oncology, University of Heidelberg ’ Dept. of Radiation Oncology, University of Marburg

Purpose: Radiosurgical treatment (RS) of acoustic neuromas is a well established treatment. However, few data are available concerning conformal fractionated radiotherapy (FT) of this tumor entity. We evaluated treatment outcome and toxicity for both treatment modalities in 4 1 patients treated at our institution between 1984 and 1997. Material and Methods: All treatments were performed using a specially adapted linear accelerator and circular collimators for convergent beam RS or multi-leaf collimators (leaf thickness I or 3mm) for multi-field RS or fractionated treatment. 22 patients (7 male, 15 female, median age 60 years, range 20-83 years) were treated radiosurgically with single doses between 7 and 28 Gray (median 15 Gy) prescribed to the 80% isodose line. Tumor volumes ranged from 0.7 to IO 5 ccm with a median volume of 3 4 ccm. The median number of isocenters was 2 (l-4 isocenters). One patient was treated by a multi-field technique (14 isocentric irregularly shaped noncoplanar tields). 19 patients (5 male, I4 female, median age 55 years, range 20-81 years) were treated with stereotactic conformal radiotherapy Median dose was 60 Gray with a median daily fraction size of 2 Gy and a median of 3 (1-4) irregularly shaped isocentric fields. Tumor volumes ranged from 0.7 to 32.4 ccm (median 15 ccm). Median follow-up was 30 months (7-149 months) for radiosurgical ?qd 30 months (2-88 months) for fractionated :xa’mpnt. Seven patients who underwent fractionated treatment had previously undergone neurosurgical resection on the contralateral side. One had undergone radiosurgery on the opposite side before Results: All tumors were locally controlled. A volume reduction of more than 20% was seen in 16% after RS and 18% following FT. Typical posttherapeutic central reduction of contrast media enhancement was found in 73% following RS after a median of 8 (3-12) months and in 63% following FT after a median of 6 (1-12) months. Temporary brainstem edema was diagnosed iv 4 patients (18%) in the RS group, none of them requiring therapy, but none in the FT group. Hearing impairment improved in 1 case (RS) and 4 cases (FT). Complete hearing loss was diagnosed in I case in the FT group but in 3 cases in the RS group (all these patients were treated with 16 Gy or more). One temporary facial nerve weakness was found after FT Among the RS group treated with 216 Gy, 4 permanent facial nerve lesions were observed with complete facial nerve paresis in 2 patients Improvement of vertigo or tinnitus was found in I patient after FT and in 3 patients treated with RS. If radiosurgical doses were ~15 Gy, no severe side effects were observed. Among this group, 6 patients (54%) showed a significant reduction of preexisting neurological dysfunction Conclusion: Radiosurgical treatment of small acoustic neuromas with doses <I 5 Gy prescribed to a volume <IO ccm results in excellent tumor controi with no relevant toxicity. For fractionated therapy, results are comparable, even if the tumor volume exceeded 10 ccm. Single dose treatment with doses >I5 Gy may cause higher toxicity. Fractionated conformal radiotherapy offers effective tumor control and low morbidity especially after contralateral neurosurgical resection of an acoustic neuroma with consecutive hearing loss and/or facial paresis.

1018 LONG-TERM RESULTS OF PROTON RADIOSURGERY AND FRACTIONATED PROTON IRRADIATION FOR VESTIBULAR scHwANNoMAs

A Mahajan MD(l), A Thornton, MD(l), E Cascio BSc(3), A KoehIer BSc(3), G Harsh MD (2), P Chapman MD(2), J Munzenrider MD(l)

Departments of Radiation Oncology(l), Neurosurgety(2), Massachusetts General Hospital, and the Harvard Cyclotron Laboratoly(3), Boston, Ma

Puroose/Obiective~ To revkew the outcome of patients with vestibular schwannomas treated with stereotactic proton irradiation, both single-fraction and fractionated, in order to establish comparative disease-control rates and morbidities. Materials & Methods: All available records of 3 1 patients treated with 160 MeV proton irradiation between 1976 - 1990 were reviewed. 19 patients (10 females and 9 males) had unilateral lesions, 12 patients (9 females and 3 males) had neurofibromatosis II. In the NF group the indication to treat was to preserve hearing in 10 patients, while in the non+@ group, the indication to treat in 4 patients was post-surgical recurrence and in 6 was post- operative residual Treatment techniques were consistent in that 25 patients were treated by one physician with a single fraction of proton irradiation. 6 patients were treated with fractionated irradiation with a combination of 160 MeV protons and 3-D planned megavoltage photons The mean dose given to the 90% isodose line (encompassing tumor) for single-fraction treatments was 3 1.4 CGE, with an average target volume of 3.8 cc. The fractionated doses varied from 57 1 to 72.0 CGE delivered at I 7-1.9 CGE/day. The mean proton cornpotent in the fractionated treatments was 72% Mean tumor diameter in the single-fraction NF group was 2.6 cm and in the non-NF group was 2.4 cm. For the fractionated group mean diameter was 2.3 cm w With a median follow-up of 10.6 years (range 0 - 19), the 1, 5, 10, and Il-year overall actuarial survivals of the group with NF were 91, 82, 63 and 42%. respectively For non-NF group the same interval actuarials were 100, 100,94 and 63%, respectively. Actuarial event-free survival (clinical/radiological progression or surgical intervention) for the patients treated with NF was 54% at 1 year and remained at 46% from 5 to I8 years. For the group with no NF, the 1, 5, and IO-year event-free survivals were 73%, 67%, and 58%, respectively. The differences between the two groups’ survivals are not statistically significant.

Analysis of hearing preservation indicates those patients with NF to have maintained useful hearing in 22% of cases - loss of serviceable hearing occurred either due to irradiation or to tumor progression, requiring surgery and consequent CN 8 resection. Of the non-NF patients, only 25% of those with pre-treatment usefil hearing (n=4) retain hearing. Comparison of irradiation regimens indicates rates of hearing preservation to be 30-40% by single-fraction and 50-60% by fractionated technique.

Facial nerve complication rates indicate in the NF group a 16% permanent deficit rate, due to probable progression of tumor in all patients. In the non-m patients, temporary CN 7 palsy occurred in 50%, with permanent deficits occurring in 16% due to tumor progression and another 16% due to irradiation damage. Single-fraction and fractionated irradiation permanent CN 7 deficit rates are 15-40% and O-10%, respectively.

Trigeminal nerve palsies occurred in 3% of patients transiently and 6% permanently after irradiation, with all patients having received fractionated treatment Of the patients with permanent CN 5 deficits, 50% had NF. Transient edema was noted radiologically in 3 patients, 1 with NF. There were no reported cases of acute hydrocephalus after the irradiation, although I5 of the 3 1 had distortion of the fourth ventricle prior to irradiation. Ataxia was present initially in 28 patients and worsened with time in 22%. Conclusions: The long-term follow-up of this mixed population of NF/non-NF acoustic neuroma patients suggests similar survival/complication rates to other surgical/irradiation techniques. Surprisingly, the relatively high doses used in this early single-fraction effort did not realize either improved control or worse complication rates compared to more contemporary series.