Hypo-fractionated stereotactic radiotherapy (HF-SRT) for peri-optic pituitary adenomas – Early results of a novel experience

Abstract

Background/Objective To report our early experience with a novel Hypo-fractionated Stereotactic Radiotherapy (HF-SRT) regimen in the treatment of pituitary adenomas located in close proximity to the optic apparatus. Methods Twelve patients were treated using HF-SRT— total doses of 35-40 Gy in 7-10 fractions (4-5 Gy/fx). Sixty seven percent received 40 Gy in 10 fractions. Doses were prescribed to the 80-95% isodose line when the technique was cone-based, and to 85-95% of the Planning Target Volume (PTV) when IMRT-based. The end-points were visual function preservation, and local control as defined by follow-up MRI and/or biochemical control. Results Median age was 44.5 years. Sixty seven percent (8/12) had secretory adenomas. Median tumor volume as 5.8 cc. Median follow-up was 18.5 months. Mean marginal tumor dose was 42.7 Gy. Mean minimum distance from the optic chiasm was 2.3 mm. Mean maximum dose to the optic apparatus was 36 Gy. Visual improvement/stabilization rate was 87.5% (7/8). Radiological local control rate was 92% (11/12), CR in 25% (3/12), PR in 33% (4/12), SD in 33% (4/12), and PD in 8% (1/12). Endocrinological response was seen in all patients with abnormal hormone levels prior to therapy (8/8). Acute toxicity included headaches (42%) and nausea (8%). One patient with a previous history of pituitary hemorrhage suffered an episode of pituitary apoplexy 2 months after HF-SRT. Another patient with history of prior full dose conventional radiotherapy 2.5 years prior to HF-SRT, developed dissection and thrombosis of the right internal carotid artery. Conclusions Early results of HF-SRT (4-5 Gy/fx) in 7-10 fractions show comparable radiological and endocrinological tumor control to conventionally fractionated radiotherapy or single fraction SRS, with excellent visual preservation. Longer follow-up is needed to ascertain efficacy and long term toxicity of this technique.