Conventionally Fractionated Stereotactic Radiotherapy for Vestibular Schwannoma: Long-Term Outcome and Cranial Nerve Function

Diana Stripp, MD
University of Pennsylvania Cancer Center
Last Modified: November 8, 2001

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Presenter: Chan, A
Presenter's Affiliation: Massachusetts Gerneral Hospital, Boston, MA
Type of Session: Scientific

Background

  • Vestibular schwannoma/acoutic neuroma comprises 8% of all primary brain tumors.
  • It?s location ? closely associated with brain stem and cranial nerve, creates great challenge for treatment.
  • Surgical outcome has shown good results with tumor < 2cm. However, for tumor >2cm, cranial nerve damage could be permenant.
  • 1945, 1st fractionated radiotherapy (RT) was done at UCSF. 1987, 1st large study on fractionated RT.

    Materials and Methods

  • 48 patients (1993-2000) with vestibular schwannoma were treated with linac accelerator-based stereotactic radiotherapy at the Massachusetts General Hospital or Brigham and Women?s Hospital.
  • 6 patients with neurofibromatosis type II, and 5 patients had intracanicular tumors only.
  • 39 patients were treated with primary radiotherapy and 9 patients were treated after primary surgical resection for persistent (n = 1) or recurrent (n = 8) disease.
  • Six patients had pre-existing facial paresis at the time of radiation (House-Brackmann class 2 in 1, class 4 in 1, class 5 in 3, and class 6 in 1).
  • The median tumor volume was 3.1 cc (range: 0.17 cc - 21.07 cc). The median dose was 54 Gy in 1.8 Gy per fraction prescribed to 95% of the isodose.
  • Computerized tomography/magnetic resonance images were used for target definition. Conformal treatment plans were generated using one isocenter and three to six non-coplanar arcs. Follow-up duration ranged from 12 to 77 months.

    Results

  • The overall local control rate (stabilization or regression of tumor) was 94%.
  • Post-radiation surgical intervention was performed in 3 patients (6%); two underwent microsurgical resection at 39 and 44 months for progressive enlargement of tumors, and one underwent shunt placement for persistent hydrocephalus and progressive disease at 6 months.
  • The rate of hearing preservation (maintenance of the pre-treatment Gardner-Robertson hearing function class or no subjective decline of hearing) was 83%.
  • All patients with pre-treatment useful hearing (Gardner-Robertson class 1 - 2) maintained useful hearing after radiation.
  • Pre-treatment normal facial and trigeminal nerve function was preserved in all cases.
  • One patient with an intracanicular tumor and a pre-treatment House-Brackmann class 2 facial dysfunction developed permanent class 5 facial weakness during the first week of radiation. Mild trigeminal toxicity was observed in one patient at 18 months after radiation.
  • There were no other complications or second cancer

    Author's Conclusions
    Stereotactic radiotherapy using a conventionally fractionated schedule results in local control rate comparable with that reported for gamma knife radiosurgery and microsurgery resection, but with a high rate of hearing preservation and a very low rate of trigeminal and facial neuropathy

    Clinical/Scientific Implications

  • Improved rate of hearing preservation and low rate of trigeminal and facial neuropathy provides a very attractive therapeutic scheme for treatment of vestibular schwannoma, if feasible with individual clinics.
  • Long term follow up is needed to evaluation late recurrence


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