Linear accelerator radiosurgery for pituitary macroadenomas

Abstract

BACKGROUND. 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. METHODS. 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. RESULTS. 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%). CONCLUSIONS. 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 γ‐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. Cancer 2006. © 2006 American Cancer Society.