Radiosurgery for acoustic neurinoma with rapid growth and relatively high staining indexes for proliferating cell nuclear antigen and MIB-1.

A 54-year-old female presented with a rapidly growing acoustic neurinoma. The tumor doubling time was 216 days or less before surgery and staining indexes for proliferating cell nuclear antigen (PCNA) and MIB-1 were relatively high (4.1% and 2.1%, respectively). The tumor was partially removed, but regrowth was detected with a tumor doubling time of 205 days. She underwent gamma knife radiosurgery for the residual tumor. The periphery of the tumor was irradiated with a dose of 15 Gy. Magnetic resonance imaging 30 months later demonstrated significant tumor shrinkage. The tumor half time following irradiation was determined to be 401 days. Neither surgery nor radiosurgery produced any additional neurological deficit or complications. Gamma knife radiosurgery can control neurinoma growth even when the tumor shows rapid growth and a relatively high growth fraction indicated by high staining indexes for PCNA or MIB-1.