Proton beam stereotactic radiosurgery of vestibular schwannomas.

Abstract

PURPOSE:

The proton beam's Bragg peak permits highly conformal radiation of skull base tumors. This study, prompted by reports of transient (30% each) and permanent (10% each) facial and trigeminal neuropathy after stereotactic radiosurgery of vestibular schwannomas with marginal doses of 16-20 Gy, assessed whether proton beam radiosurgery using a marginal dose of only 12 Gy could control vestibular schwannomas while causing less neuropathy.

METHODS AND MATERIALS:

Sixty-eight patients (mean age 67 years) were treated between 1992 and 1998. The mean tumor volume was 2.49 cm(3). The dose to the tumor margin (70% isodose line) was 12 Gy. The prospectively specified follow-up consisted of neurologic evaluation and MRI at 6, 12, 24, and 36 months.

RESULTS:

After a mean clinical follow-up of 44 months and imaging follow-up of 34 months in 64 patients, 35 tumors (54.7%) were smaller and 25 (39.1%) were unchanged (tumor control rate 94%; actuarial control rate 94% at 2 years and 84% at 5 years). Three tumors enlarged: one shrank after repeated radiosurgery, one remained enlarged at the time of unrelated death, and one had not been imaged for 4 years in a patient who remained asymptomatic at last follow-up. Intratumoral hemorrhage into one stable tumor required craniotomy that proved successful. Thus, 97% of tumors required no additional treatment. Three patients (4.7%) underwent shunting for hydrocephalus evident as increased ataxia. Of 6 patients with functional hearing ipsilaterally, 1 improved, 1 was unchanged, and 4 progressively lost hearing. Cranial neuropathies were infrequent: persistent facial hypesthesia (2 new, 1 exacerbated; 4.7%); intermittent facial paresthesias (5 new, 1 exacerbated; 9.4%); persistent facial weakness (2 new, 1 exacerbated; 4.7%) requiring oculoplasty; transient partial facial weakness (5 new, 1 exacerbated; 9.4%), and synkinesis (5 new, 1 exacerbated; 9.4%).

CONCLUSION:

Proton beam stereotactic radiosurgery of vestibular schwannomas at the doses used in this study controls tumor growth with relatively few complications.

• Authors: Griffith R Harsh, Allan F Thornton, Paul H Chapman, Marc R Bussiere, James D Rabinov, Jay S Loeffler
• Journal: International journal of radiation oncology, biology, physics (Int J Radiat Oncol Biol Phys) Vol. 54 Issue 1 Pg. 35-44 (Sep 01 2002) ISSN: 0360-3016 [Print] United States
• PMID: 12182972 (Publication Type: Journal Article)

Topics

• Adult
• Aged
• Aged, 80 and over
• Female
• Follow-Up Studies
• Humans
• Magnetic Resonance Imaging
• Male
• Middle Aged
• Neuroma, Acoustic (pathology, surgery)
• Patient Satisfaction
• Radiosurgery (methods)