Fractionated stereotactic radiotherapy for acoustic neuromas: preservation of function versus size.

For larger acoustic neuromas the preservation of cranial nerve function following radiosurgery remains a challenge. Fractionated stereotactic radiotherapy (FSR) for acoustic neuromas offers both higher total tumour dose (Gy) and potential sparing of the facial motor, sensory and auditory cranial nerves. Eighty consecutive patients (45 M, 35 F) (age 56.8+/-1.7 years) received FSR for AN and have a median follow up of 1.1 years. A prospective schedule permitted increased fractionation vs. size. For FSR 70 patients having AN < 3.0 cm in diameter had 5 daily fractions of 5 Gy (25 Gy total) and 10 patients having AN > or = 3 cm had 10 daily fractions of 3 Gy (30 Gy total). All treatments were prescribed to the 80% isodose and given via the dedicated 10 MeV accelerator. For both the larger and smaller AN, the percentage decrease in volume was similar. No tumour increased in size, no patient developed facial weakness and hearing was preserved. Using size-dependent fractionation, FSR may result in both tumour control and preservation of normal cranial nerve functions for both large and small AN.