Long term results of radiosurgery for vestibular schwannomas

Abstract

Radiosurgery is either a primary or an adjunct management approach used to treat patients with vestibular schwannomas. The goals are long-term tumour growth control, maintenance of cranial nerve function and prevention of new neurologic deficiencies. We sought to determine long-term outcomes measuring the potential benefits against the neurological risks of radiosurgery.

Methods: 278 patients with vestibular schwannomas underwent Gamma Knife radiosurgery as a treatment modality for from April 1992 to November 2001. The long-term results of 60 patients were evaluated who received radiosurgery as primary treatment. 12 cases presented with previously performed subtotal microsurgical resection or recurrence of disease (12-96 months, median 39). The median treatment volume was 3.8 ccm and the median dose to the tumour margin was 12 Gy. The median patient follow-up time was 88 months (range 72-114 months).

Results: Four tumours progressed after primary radiosurgery. Tumour control rate was 93%. Useful hearing (Gardner-Robertson I/II) was preserved in 16 patients (55%). Clinical neurological improvement occured in 36 patients (60%). Adverse effects comprised neurological symptoms (incomplete facial palsy) (House-Brackman II/III) in five cases (three recovered completely), mild trigeminal neuropathy in three cases, and morphological changes displaying rapid enlargement of preexisting macrocysts in two patients and tumour growth in two other ones. Microsurgical resection was performed in three cases (5%) and one patient underwent a shunting procedure because of hydrocephalus formation. In patients who had undergone previous microsurgery, neither new cranial nerve deficit nor any tumour growth was observed.

Conclusions: Radiosurgery performed with current techniques proved to be an effective method for growth control of vestibular schwannomas with both a low mortality rate and a good quality of life. An increasing percentage of patients will undergo radiosurgery as accessibility to this alternative increases, and more data regarding long-term follow-up are available. It is a post-operative complementary treatment for partially removed tumours. Accordingly, radiosurgery is a useful method for the management of properly selected patients.

Zusammenfassung

Die Radiochirurgie ist eine primäre oder zusätzliche Behandlungsmöglichkeit für Patienten mit Vestibularisschwannomen. Ziele sind Wachstumskontrolle des Tumors, Erhalt der Hirnnervenfunktion und Vermeidung neuer Defizite. In dieser Studie untersuchten wir die Langzeitergebnisse.

Methode: Die Gamma-Knife-Radiochirurgie wurde als Behandlung an 278 Patienten mit Vestibularisschwannomen von April 1992 bis November 2001 durchgeführt. Ausgewertet wurden 60 Patienten mit primärer Behandlung und 12 Patienten mit adjuvanter Therapie 12-96 Monate (median 39 Monate) nach mikrochirurgischer Vorbehandlung und/oder Rezidivtumor. Das mediane Behandlungsvolumen betrug 3,8 ccm und die mediane Dosis auf den Tumorrand war 12 Gy. Der mediane Patient wurde 88 Monate beobachtet (72-114 Monate).

Ergebnisse: Vier Tumoren zeigten ein postradiochirurgisches Wachstum. Die Tumorkontrolle war in 93% gegeben. Ein gebrauchsfähiges Gehör (Gardner-Robertson I/II) wurde in 16 (von 29) Patienten (55%) erhalten, eine neurologische Besserung trat in 36 Fällen (60%) auf. Nebenwirkungen beinhalteten eine inkomplette Fazialis-Parese (House-Brackman II/III) in 5 Fällen (3 vorübergehend), eine leichte Trigeminus-Neuropathie 3-mal und die rasche Erweiterung von vorbestehenden Zysten sowie Tumorwachstum in je 2 Fällen. Eine mikrochirurgische Nachresektion erfolgte in 3 Fällen (5%) und eine Shuntimplantation in einem Fall.

Die Radiochirurgie ist eine wirksame Methode zur Behandlung von Vestibularisschwannomen mit niedriger Morbidität und fehlender Mortalität. Eine zunehmende Zahl von Patienten wird aufgrund der verbesserten Verfügbarkeit und der größeren Langzeitkollektive der Radiochirurgie diese Behandlungsmodalität erfahren. In ausgewählten Fällen ist sie die Alternative zur Mikrochirurgie und kann bei Rest- und Rezidivtumoren Ergänzung zur Mikrochirurgie sein.

Key words

Acoustic neurinoma - Conformity Index - Cranial nerve preservation - Radiobiology - Residual tumours - Stereotaxis

Schlüsselwörter

Akustikusneurinom - Hirnnervenfunktion - Konformitätsindex - Radiobiologie - Resttumoren - Stereotaxie

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