Adjuvant versus on-progression Gamma Knife radiosurgery for residual nonfunctioning pituitary adenomas: a matched-cohort analysis

Abstract

Objective: Radiological progression occurs in 50%-60% of residual nonfunctioning pituitary adenomas (NFPAs). Stereotactic radiosurgery (SRS) is a safe and effective management option for residual NFPAs, but there is no consen-sus on its optimal timing. This study aims to define the optimal timing of SRS for residual NFPAs. Methods: This retrospective, multicenter study involved 375 patients with residual NFPAs managed with SRS. The patients were divided into adjuvant (ADJ;treated for stable residual NFPA within 6 months of resection) and progression (PRG) cohorts (treated for residual NFPA progression). Factors associated with tumor progression and clinical deteriora-tion were analyzed.Results: Following propensity-score matching, each cohort consisted of 130 patients. At last follow-up, tumor con-trol was achieved in 93.1% of patients in the ADJ cohort and in 96.2% of patients in the PRG cohort (HR 1.6, 95% CI 0.55-4.9, p = 0.37). Hypopituitarism was associated with a maximum point dose of > 8 Gy to the pituitary stalk (HR 4.5, 95% CI 1.6-12.6, p = 0.004). No statistically significant difference was noted in crude new-onset hypopituitarism rates (risk difference [RD] = -0.8%, p > 0.99) or visual deficits (RD = -2.3%, p = 0.21) between the two cohorts at the last follow-up. The median time from resection to new hypopituitarism was longer in the PRG cohort (58.9 vs 29.7 months, p = 0.01).Conclusions: SRS at residual NFPA progression does not appear to alter the probability of tumor control or hormon-al/visual deficits compared with adjuvant SRS. Deferral of radiosurgical management to the time of radiological progres- sion could significantly prolong the time to radiosurgically induced pituitary dysfunction. A lower maximum point dose (< 8 Gy) to the pituitary stalk portended a more favorable chance of preserving pituitary function after SRS.