Dosimetric factors associated with pituitary function after Gamma Knife Surgery (GKS) of pituitary adenomas.
OBJECTIVE
Gamma Knife Surgery (GKS) can be an adjunctive option to surgery in the case of pituitary adenomas. The effect of dosimetric variables on the incidence of new anterior pituitary deficits after GKS requires better definition.


METHODS
This retrospective study considered 130 patients with a follow up after GKS >6 months. The diagnosis was nonfunctioning pituitary adenoma (NFPA) in 68 patients and secreting pituitary adenoma (SPA) in 62 patients. Median margin dose was 15/25 Gy for NFPA and SPA, respectively. The endocrinological median follow-up was 60 months. Hypopituitarism was defined as a new pituitary deficit in (at least) one of the three hormonal axes (hypogonadism, hypothyroidism and hypoadrenalism). The predictive value of clinical/dosimetric parameters was tested by univariate/multivariate analyses.


RESULTS
Sixteen patients (12.3%) showed a new pituitary deficit in one or more axes. Multivariate analysis confirmed that the mean dose to the stalk/pituitary and the amount of healthy tissue within the high dose region were strong independent predictors of pituitary dysfunction; their best cut-off values were around 15.7 Gy, 7.3 Gy and 1.4 cm(3), respectively.


CONCLUSIONS
Our data showed a dose-dependent incidence of new hormonal deficits after GKS for pituitary adenoma. During planning definition, the risk of hypopituitarism could be reduced using the outlined safe dose-volume values.
Medical Physics Department, San Raffaele Scientific Institute, Milan, Italy.
Gianluisa
G
Sicignano
Marco
M
Losa
Antonella
A
del Vecchio
Giovanni Mauro
GM
Cattaneo
Piero
P
Picozzi
Angelo
A
Bolognesi
Pietro
P
Mortini
Riccardo
R
Calandrino
D000236:Adenoma / Q000503:physiopathology / Q000601:surgery*; D004307:Dose-Response Relationship, Radiation; D005260:Female; D006801:Humans; D007018:Hypopituitarism / Q000209:etiology*; D008297:Male; D008875:Middle Aged; D010911:Pituitary Neoplasms / Q000503:physiopathology / Q000601:surgery*; D016634:Radiosurgery; D011880:Radiotherapy Planning, Computer-Assisted; D012189:Retrospective Studies