Fractionated stereotactic radiotherapy for large and invasive non-functioning pituitary adenomas: long-term clinical outcomes and volumetric MRI assessment of tumor response.

Design: Fractionated stereotactic radiotherapy (FSRT) is frequently employed for the treatment of residual or recurrent pituitary adenomas. We describe our use of FSRT for the treatment of large, invasive, nonfunctioning pituitary adenomas (NFPAs). Methods: Sixty-eight patients with a large residual or recurrent NFPAs were treated between April 2004 and December 2012, including 39 males and 29 females (median age 51 years). Visual defects were present in 34 patients, consisting of visual field defects (n=31) and/or reduced visual acuity (n=12). Forty-five patients had evidence of partial or total hypopituitarism before FSRT. For most of the patients, the treatment was delivered through 5-10 noncoplanar conformal fixed fields using a 6-MV linear accelerator to a dose of 45 Gy in 25 fractions. Results: At a median follow-up of 75 months (range 12-120 months), the 5-year and 10-year actuarial local control were 97% and 91%, respectively, and overall survival 97% and 93%, respectively. Forty-nine patients had a tumor reduction, 16 remained stable, and 3 progressed. The relative tumor volume reduction measured using three-dimensional (3-D) magnetic resonance imaging (MRI) was 47%. The treatment was well tolerated with minimal acute toxicity. Eighteen patients developed partial or complete hypopituitarism. The actuarial incidence of new anterior pituitary deficits was 40% at 5 years and 72% at 10 years. No other radiation-induced complications occurred. Conclusions: Our results suggest that FSRT is an effective treatment for large or giant pituitary adenomas with low toxicity.