Recurrence Of Pituitary Adenomas Following Gamma Knife Radiosurgery

Piero Picozzi, MD1, Marco Losa2, Alberto Franzin3, Micol Angela Valle2, Carlo Serra2, Antonella Del Vecchio4, Lorenzo Gioia2, Angelo Bolognesi5, Pietro Mortini2

1Department of Neurosurgery, IRCCS San Raffaele 2Gamma Knife Unit 3Mi, Italy 4Milan, Italy 5IRCCS San Raffaele Dept of Radiation Oncology

Keywords: pituitary adenoma, hormone dysfunction, gamma knife, cavernous sinus, outcome

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     The goal of Gamma Knife radiosurgery (GKRS) in pituitary adenomas is the control of tumor growth and endocrinopathy. Regrowth of a pituitary adenoma following GKRS is a rare event.
     Aim of this study is to investigate the causes of failure in the control of adenoma growth and possible pitfalls of the treatment.
     Between 1994 and 2008, 336 patients (131 men, 39%, and 205 women, 61%; mean age 45.7±0.7 years) with a diagnosis of non functioning pituitary adenoma (NFPA) in 156 pz (39%) or secreting pituitary adenoma (SPA) in 180 pz (61%). All patients had surgical treatment in our center and were treated with GKRS for residual pituitary tumor. No patient had previously received external fractionated radiotherapy (EFRT).
     Medial marginal dose was 15.5±0.2 Gy (range 12-25 Gy) for NFPA and 22.2±0.3 Gy (range 12-25 Gy) for SPA at 50% isodose; the dose to the optic pathways was kept below 10 Gy. GKRS was performed to prevent growth of residual tumor in all cases and with the goal of control the endocrinopathy in secreting adenomas. Baselines and follow-up studies was focused on MRI and volume measurement to detect tumor progression.
     The mean follow-up after GKRS was 55.5±2.2 months (range 6-177 months); NFPA 46.6±2.9 month and SPA 68.2±3.8. There were 16 recurrences (4.8 %). The 5 years recurrence-free survival was 95.9% (95% CI, 93.0-98.7%) and 8 years recurrence free survival was 92.7% (95% CI, 88.2-97.2%). The pattern of recurrence was out of the field of previous radiosurgery in 12 (75%) cases while in the field in 4 (25%) cases: in 3 of the in-field recurrence the tumor had an aggressive behaviour. In 9 cases a new GKRS was performed as the only salvage treatment while in the other cases a a combination of surgery, EFRT, GKRS and medical therapy was utilized to control tumor growth.
     This is a retrospective study.
     Most of recurrences were caused by unrecognized components of residual adenoma at the time of the first treatment.
     Current doses were found to be adequate for growth control, since in only 4 patient (1,2%) we detected an infield recurrence following GKRS.


Project Roles:

P. Picozzi (), M. Losa (), A. Franzin (), M. Valle (), C. Serra (), A. Del Vecchio (), L. Gioia (), A. Bolognesi (), P. Mortini ()