Modern Linear Accelerator-Based Radiotherapy Is Safe and Effective in the Treatment of Secretory and Nonsecretory Pituitary Adenomas

Background: Adjuvant radiotherapy (RT) can help achieve local control (LC) and reduce hormonal overexpression for pituitary adenomas (PAs). Prior reports involved Gamma Knife or older linear accelerator (LINAC) techniques. The aim of this study was to report long-term outcomes for modern LINAC RT.

Methods: Institutional retrospective review of LINAC RT for PAs with minimum 3 years of magnetic resonance imaging follow-up was performed. Hormonal control was defined as biochemical remission in absence of medications targeting hormone excess. LC defined using Response Evaluation Criteria in Solid Tumors on surveillance magnetic resonance imaging. Progression-free survival defined as time alive with LC without return of or worsening hormonal excess from secretory PA. Kaplan-Meier and Cox proportional hazard models used.

Results: From 2003 to 2017, 140 patients with PAs (94 nonsecretory, 46 secretory) were treated with LINAC RT (105 fractionated RT, 35 radiosurgery) with median follow-up of 5.35 years. Techniques included fixed gantry intensity-modulated radiotherapy (51.4%), dynamic conformal arcs (9.3%), and volumetric modulated arc therapy (39.3%). Progression-free survival at 5 years was 95.3% for secretory tumors and 94.8% for nonsecretory tumors. Worse progression-free survival was associated with larger planning target volume on multivariable analysis (hazard ratio 2.87, 95% confidence interval 1.01-8.21, P = 0.049). Hormonal control at 5 years was 50.0% and associated with higher dose to tumor (hazard ratio 1.05, 95% confidence interval 1.02-1.09, P = 0.005) and number of surgeries (hazard ratio 1.74, 95% confidence interval 1.05-2.89, P = 0.032). Patients requiring any pituitary hormone replacement increased from 57.9% to 70.0% after RT.

Conclusions: Modern LINAC RT for patients with PAs was safe and effective for hormonal control and LC. No difference in LC was noted for functional versus nonfunctional tumors, possibly owing to higher total dose and daily image guidance.