LAUSR

OBJECTIVE Adjuvant radiotherapy (RT) can help achieve local tumor control (LC) and reduce hormonal overexpression for pituitary adenomas (PAs). Prior reports involved Gamma Knife or older LINAC techniques. We report on long-term outcomes for modern LINAC RT. METHODS Institutional retrospective review of LINAC RT for PAs with minimum 3 years MRI follow-up. Hormonal control defined as biochemical remission in absence of medications targeting hormone excess LC defined using RECIST on surveillance MRIs. Progression Free Survival (PFS) defined as time alive with LC and without return of or worsening hormonal excess from secretory PA. Kaplan-Meier method and Cox proportional hazard models used. RESULTS From 2003-2017, 140 patients with PAs (94 non-secretory, 46 secretory) were treated with LINAC RT (105 fractionated, 35 radiosurgery) with mFU of 5.35 years. Techniques included fixed gantry IMRT (51.4%), DCA (9.3%), and VMAT (39.3%). PFS at 5-years was 95.3% for secretory tumors and 94.8% for non-secretory tumors. Worse PFS associated with larger PTV on MVA (HR 2.87, 95% CI 1.01 - 8.21, p=0.049). Hormonal control at 5 years was 50.0% and associated with higher dose to the tumor (HR 1.05, 95% CI 1.02 -1.09, p=0.005) and number of surgeries (HR 1.74, 95% CI 1.05-2.89, p=0.032). Patients requiring any pituitary hormone replacement increased from 57.9% to 70.0% after radiotherapy. CONCLUSION Modern LINAC RT for patients with PAs was safe and effective for hormonal control and LC. Notably, no difference in LC was noted for functional versus non-functional tumors possibly due to higher total dose and daily image guidance.