Long-Term Outcome of Nonfunctioning and Hormonal Active Pituitary Adenoma After Gamma Knife Radiosurgery

Stereotactic radiosurgery (SRS), particularly Gamma Knife radiosurgery (GKRS) is an established treatment option for residual and recurrent pituitary adenoma tumors. It helps in the preservation of surrounding normal neuronal, vascular, and hormone-producing structures and causes fewer neurologic deficits. The aim of this research was to evaluate the efficacy and define the role of GKRS in the treatment of nonfunctioning (NFA) and hormonal active (HAA) pituitary adenoma.

A retrospective analysis of 111 patients with histologically proven pituitary adenoma who underwent GKRS treatment at Louisiana State University Health Sciences Center, Shreveport, Louisiana, USA, over a 17-year period was conducted presented. The clinical and radiologic data were collected from the database. The tumors were categorized into NFA and HAA based on the endocrinology profile. The relevant statistical analysis was conducted with SPSS software, version 22.0.

The median age of the patients was 58 years. The study comprised 87 patients with NFA and 24 patients with HAA tumors. Thirty-eight patients (34.2%) had hypopituitarism symptoms, and 8 patients (7%) had panhypopituitarism symptoms. The mean tumor volume before to GKRS was 3.8 cm³. Suprasellar and cavernous extension of the tumor was noted in 28 patients (25.2%) and 34 (30.6%) patients, respectively. We observed >70% reduction in the size of tumors in the shrinkage cohort after GKRS; the median time for shrinkage was 48.4 months. However, increase in tumor size was noted in the progression cohort (pre-GKRS 3.8 cm³ vs. post-GKRS 6.5 cm³). Seventy patients (63.1%) had neurologic improvement, and 26 patients (23.4%) had endocrinologic worsening after GKRS.

GKRS plays a significant role in the treatment of NFA and HAA. It affords a high rate of tumor control and offers a low risk of collateral neurologic or endocrine axis injury. Our study shows that control of tumor growth was achieved in 90% of patients, shrinkage of tumor in 54%, and arrest of progression in 36% after GKRS treatment. The biochemical remission rate in growth hormone secreting adenoma was 57%, in adrenocorticotropic hormone adenoma 67%, and prolactinoma 40%. Age below 50 years and tumor volume less than 5 cm³ were associated with a favorable radiosurgical outcome.