Linear accelerator radiosurgery for pituitary macroadenomas

Abstract

A prospective study was conducted to assess the efficacy and side effects of linear accelerator (LINAC)-based radiosurgery (RS) performed with a reduced dose of therapeutic radiation for patients with surgically inaccessible pituitary macroadenomas. From August 1990 through January 2004, 175 patients with pituitary macroadenomas were treated with LINAC-RS according to a prospective protocol. To minimize the risk for radiation-induced damage of the pituitary function, the therapeutic dose to be applied was limited to 20 grays. Among 175 patients, 142 patients who had a minimum follow-up of 12 months (mean +/- standard deviation, 81.9 +/- 37.2 months) were included in the current study. The local tumor control rate was 96.5%, and the tumor response rate was 32.4%. The mean time (+/- standard deviation) from LINAC-RS to normalization of pathologic hormone secretion was 36.2 +/- 24.0 months. The probability for normalization was 34.3% at 3 years and 51.1% at 5 years. The frequency of endocrine cure (defined as the normalization of hormone secretion without specific medication intake) was 35.2% (mean +/- standard deviation time to cure, 42.1 +/- 25.0 months). Patients with Cushing disease had a statistically significant greater chance of achieving a cure (P = .001). Side effects of LINAC-RS were deterioration of anterior pituitary function (12.3%), radiation-induced tissue damage (2.8%), and radiation-induced neuropathy (1.4%). LINAC-RS using a lower therapeutic radiation dose achieved local tumor control and normalization or cure of hormone secretion comparable to the results achieved with gamma-knife RS. Compared with the latter, the time to normalization or endocrine cure was delayed, most probably as a result of dose reduction. However, the lower therapeutic radiation dose did not prevent radiation-induced damage of pituitary function completely.