Hypofractionated CyberKnife radiosurgery for perichiasmatic pituitary adenomas: early results.
OBJECTIVE
Radiation therapy is recommended for pituitary tumors that are refractory to surgical and medical therapies. The efficacy of single-fraction radiosurgery is established for these lesions, but lesions within 3 mm of the optic pathway cannot be safely treated with doses higher than 8 to 10 Gy. We hypothesized that the optic nerve will tolerate 5 consecutive daily radiosurgery fractions of 500 cGy with effective tumor control.


METHODS
We reviewed our first 20 patients with recurrent or residual pituitary adenomas within 3 mm of the optic chiasm treated with the CyberKnife radiosurgery system (Accuray, Inc., Sunnyvale, CA). Tumors were treated with a mean coverage of 97 +/- 2.2% (range, 89.8-99.7%), a mean conformity index of 1.3 +/- 0.2 (range, 1.1-1.6), and a mean treatment isodose line of 74.5 +/- 6.6% (range, 60-86%). The primary end point was an interim analysis of visual preservation, and secondary end points were radiographic and endocrinological tumor control.


RESULTS
The mean follow-up period for visual field testing was 26.6 +/- 10.5 months (range, 10.6-41 months). The vision of all 14 patients with intact preoperative vision remained intact. Of the 5 patients with impaired vision, 2 remained stable, and 3 improved. No patient's vision deteriorated. The mean radiographic follow-up was 29.3 +/- 8.6 months (range, 10.2-40.5 months). On magnetic resonance imaging, 12 tumors were stable, 8 were smaller, and none enlarged.


CONCLUSIONS
This preliminary study establishes that the optic nerve and chiasm tolerate CyberKnife hypofractionated radiosurgery of 5 x 500 cGy to perichiasmatic pituitary adenomas. Early data suggest that this dosing paradigm may achieve satisfactory radiographic and endocrinological tumor control for these challenging lesions, but longer follow-up is necessary to confirm these results.
Killory
Brendan D
BD
Division of Neurological Surgery, Barrow Neurological Institute, St. Joseph's Hospital and Medical Center, Phoenix, Arizona 85013-4496, USA.
Kresl
John J
JJ
Wait
Scott D
SD
Ponce
Francisco A
FA
Porter
Randall
R
White
William L
WL
D000293:Adolescent; D000328:Adult; D000368:Aged; D005260:Female; D006801:Humans; D008279:Magnetic Resonance Imaging; D008297:Male; D008875:Middle Aged; D009364:Neoplasm Recurrence, Local / Q000601:surgery; D018365:Neoplasm, Residual / Q000601:surgery; D009897:Optic Chiasm / Q000528:radiation effects / Q000601:surgery; D010902:Pituitary Gland / Q000528:radiation effects; D010911:Pituitary Neoplasms / Q000601:surgery*; D016634:Radiosurgery / Q000009:adverse effects*; D012189:Retrospective Studies; D014787:Vision Tests; D014785:Vision, Ocular / Q000528:radiation effects*