Symptomatic outcomes in relation to tumor expansion after fractionated stereotactic radiation therapy for vestibular schwannomas: single-institutional long-term experience.
OBJECTIVE
The effect of transient tumor expansion after conventionally fractionated stereotactic radiation therapy (SRT) on the symptomatic outcomes is not well-known.


METHODS
This study enrolled 201 consecutive patients who received SRT for vestibular schwannoma. A conventional fractionation schedule was applied in 194 patients (97%), and 142 (71%) received a total dose of 50 Gy. The median follow-up time was 72 months.


RESULTS
The maximum diameter was 9 mm or less in 13 patients, 10-19 mm in 79 patients, 20-29 mm in 87 patients, and 30 mm or greater in 22 patients. At presentation, tumor size of 20 mm or greater was significantly associated with loss of serviceable hearing and trigeminal neuropathy. After SRT, tumor expansion was observed in 42 patients (21%). By tumor size, tumor expansion was observed in 0%, 11.4%, 25.6%, and 50% of patients with tumors of 9 mm or less, 10-19 mm, 20-29 mm, and 30 mm or greater, respectively, in diameter. The tumor expansion was significantly associated with an increased risk of hydrocephalus requiring shunt placement (P=.004), loss of serviceable hearing (P=.0064), and worsening of facial (P<.0001) and trigeminal nerve (P<.0001) functions. Spontaneous tumor shrinkage was observed in 29 of those 42 patients, mostly within 2 years after the expansion, and the majority of the worsened symptoms except for hearing resolved once the tumor had shrunk. As a result, salvage surgical resection for symptomatic relief was required in only 5% of patients.


CONCLUSIONS
Fractionated SRT could be safely applied even for medium- to large-sized (≥20 mm) tumors. However, greater knowledge of the risks and consequences, including transient symptomatic worsening, and the time span of expansion will be required for the follow-up of patients after SRT to avoid unnecessary surgical intervention.
Department of Radiation Medicine, Hokkaido University Graduate School of Medicine, Sapporo, Japan. h-aoyama@med.niigata-u.ac.jp
Hidefumi
H
Aoyama
Shunsuke
S
Onodera
Norihito
N
Takeichi
Rikiya
R
Onimaru
Shunsuke
S
Terasaka
Yutaka
Y
Sawamura
Hiroki
H
Shirato
D000293:Adolescent; D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D018450:Disease Progression; D004244:Dizziness / Q000601:surgery; D019583:Dose Fractionation, Radiation; D005155:Facial Nerve Diseases / Q000209:etiology; D005260:Female; D006309:Hearing / Q000528:radiation effects; D034381:Hearing Loss / Q000209:etiology; D006801:Humans; D006849:Hydrocephalus / Q000209:etiology / Q000628:therapy; D008297:Male; D008875:Middle Aged; D015999:Multivariate Analysis; D009365:Neoplasm Regression, Spontaneous; D009464:Neuroma, Acoustic / Q000473:pathology / Q000601:surgery*; D016634:Radiosurgery / Q000009:adverse effects / Q000379:methods*; D016879:Salvage Therapy / Q000379:methods / Q000706:statistics & numerical data; D014012:Tinnitus / Q000209:etiology / Q000601:surgery; D014276:Trigeminal Nerve / Q000528:radiation effects; D020433:Trigeminal Nerve Diseases / Q000209:etiology; D047368:Tumor Burden; D055815:Young Adult