Early Versus Delayed Fractionated Stereotactic Radiotherapy for Nonfunctioning Pituitary Adenoma

BACKGROUND: Fractionated stereotactic radiotherapy (FSRT) is a common modality used to treat pituitary ade-nomas with good control rates. It is not known whether FSRT should be performed early or delayed until progres-sion occurs. We compared FSRT in treating nonfunctional pituitary adenomas (NFPA) as an adjuvant (ADJ) or on-progression (PRG) therapy. -METHODS: A retrospective review of patients who un-derwent FSRT for an NFPA between January 2004 and December 2022 at a single institution was performed. We compared endocrinologic, ophthalmologic, and radio-graphic outcomes in FSRT delivered as ADJ and PRG treatment.RESULTS: Seventy-five patients were analyzed, with a median follow-up of 53 months. FSRT was administered to 35 and 40 patients as ADJ and PRG, with a median time to treatment of 5.5 and 40 months, respectively. The tumor control rate was 94.3% for ADJ and 95.0% for PRG. Treatment resulted in 4 (11.4%) versus 7 (17.5%) new endocrinopathies and 2 (5.7%) versus 1 (2.5%) new visual deficits for ADJ versus PRG. A survival analysis of time to new endocrinopathy showed no difference between the 2 cohorts. The median time from surgery to new endocrinopathy was significantly different between ADJ and PRG, at 15.5 and 102.0 months, respectively. -CONCLUSIONS: FSRT is effective in treating NFPA for residual and progressive tumors, with excellent tumor control rates and a low risk of developing new endo-crinopathies and visual deficits. Delaying treatment delayed the development of new endocrinopathies, sug-gesting that observation with FSRT on tumor progression may delay the onset of hypopituitarism and maintain similar effectiveness in tumor control.