Pituitary neuroendocrine tumors treated with stereotactic radiosurgery.

Purpose: Pituitary neuroendocrine tumors (pitNETs) are benign tumors that may recur after surgical resection or persist following medical management. The objective of this study was to evaluate outcomes and toxicities of patients with pitNETs treated with stereotactic radiosurgery (SRS) at a single institution.

Methods: We completed a retrospective, single-institution study of patients with pitNETs treated with frame-based, single-fraction, cobalt-60 SRS between September 2005 and June 2023. The primary endpoint was local tumor control. Secondary endpoints included endocrine control (for functional tumors), overall survival, and toxicities.

Results: A total of 88 lesions in 83 patients were treated with SRS. Most lesions (70%) were non-functional tumors. Of the 26 functioning tumors, 6 patients achieved endocrine remission with SRS alone (23%), and the remainder achieved remission with combined medical management. With a median patient follow-up of 4.7 years, no local tumor recurrences were observed with an estimated local control probability of 100%. Two- and five-year overall survival estimates were 97% (95% confidence interval [CI] 89-99) and 95% (95% CI 84-98), respectively. Causes of death were unrelated to PitNET or SRS. Twelve patients (14%) developed hypopituitarism after SRS. Despite the 34 lesions that were ≤ 3 mm from optic structures, no patients developed any optic neuropathy or visual decline post SRS.

Conclusions: SRS is a highly effective modality for recurrent or residual pitNETs. This study observed a local control of 100% with no cases of optic toxicities after a median follow-up of 4.7 years. These observed findings suggest that dose de-escalation may be possible for future treatment of pitNETs.