Hormonal and radiologic outcomes after gamma knife radiosurgery for nonfunctioning pituitary adenomas

Gamma knife radiosurgery (GKRS) is an established treatment option for residual and recurrent nonfunctioning pituitary adenoma (NFPA). This investigation assessed hormonal and radiologic outcomes after adjuvant and primary GKRS for NFPAs.

This retrospective study included 252 patients with NFPA who underwent GKRS at a single center between 2005 and 2016. GKRS was performed as adjuvant procedure in 216 (85.8%) patients and as primary procedure in 36 (14.2%) patients. Characteristics of these two groups were compared.

Mean age was comparable between adjuvant and primary GKRS groups (48.3 ± 12.6 vs. 52.2 ± 13.2 years, respectively, p > 0.05). Adjuvant GKRS and primary GKRS groups were similar in terms of the mean prescribed radiation dose and tumor volume (15.1 ± 2.7 vs. 15.3 ± 1.9 Gy and 4.2 ± 3.6 vs. 3.1 ± 2.5 cm³, respectively, p > 0.05 for both). The rate of endocrine deficiency during 5-year follow-up showed similar trend in adjuvant and primary GKRS groups (3.7%, 8.7%, and 14.8% vs. 5.6%, 13.9%, and 27.8% at first, third, and fifth year time points, respectively). Tumor control rates were also similar (98.6%, 96.3%, and 93% vs. 100%, 97.3%, and 94.5% at first, third, and fifth year time points, respectively). In both groups, tumor volume >5 cm³ was associated with higher rate of hypopituitarism and tumor progression.

GKRS was effective both as adjuvant and primary procedure in patients with NFPA. Radiation dose of ≤13.5 Gy was associated with lower tumor control rate and tumor volume >5 cm³ was associated with higher rates of hypopituitarism and tumor progression.