Is it possible to avoid hypopituitarism after irradiation of pituitary adenomas by the Leksell gamma knife?
OBJECTIVE
Radiation therapy is one of the treatment options for pituitary adenomas. The most common side effect associated with Leksell gamma knife (LGK) irradiation is the development of hypopituitarism. The aim of this study was to verify that hypopituitarism does not develop if the maximum mean dose to pituitary is kept under 15 Gy and to evaluate the influence of maximum distal infundibulum dose on the development of hypopituitarism.


METHODS
We followed the incidence of hypopituitarism in 85 patients irradiated with LGK in 1993-2003. The patients were divided in two subgroups: the first subgroup followed prospectively (45 patients), irradiated with a mean dose to pituitary <15 Gy; the second subgroup followed retrospectively 1993-2001 and prospectively 2001-2009 (40 patients), irradiated with a mean dose to pituitary >15 Gy. Serum TSH, free thyroxine, testosterone or 17β-oestradiol, IGF1, prolactin and cortisol levels were evaluated before and every 6 months after LGK irradiation.


RESULTS
Hypopituitarism after LGK irradiation developed only in 1 out of 45 (2.2%) patients irradiated with a mean dose to pituitary <15 Gy, in contrast to 72.5% patients irradiated with a mean dose to pituitary >15 Gy. The radiation dose to the distal infundibulum was found as an independent factor of hypopituitarism with calculated maximum safe dose of 17 Gy.


CONCLUSIONS
Keeping the mean radiation dose to pituitary under 15 Gy and the dose to the distal infundibulum under 17 Gy prevents the development of hypopituitarism following LGK irradiation.
Third Department of Medicine, First Medical Faculty, Charles University, Czech Republic.
Josef
J
Marek
Jana
J
Jezková
Václav
V
Hána
Michal
M
Krsek
L'ubomíra
L
Bandúrová
Ladislav
L
Pecen
Vilibald
V
Vladyka
Roman
R
Liscák
D000236:Adenoma / Q000097:blood / Q000601:surgery*; D000293:Adolescent; D000328:Adult; D000368:Aged; D000704:Analysis of Variance; D004958:Estradiol / Q000097:blood; D005260:Female; D005640:Follicle Stimulating Hormone / Q000097:blood; D006801:Humans; D006854:Hydrocortisone / Q000097:blood; D007018:Hypopituitarism / Q000097:blood / Q000209:etiology*; D007334:Insulin-Like Growth Factor I; D008297:Male; D008875:Middle Aged; D010902:Pituitary Gland / Q000601:surgery; D010911:Pituitary Neoplasms / Q000097:blood / Q000601:surgery*; D011388:Prolactin / Q000097:blood; D016016:Proportional Hazards Models; D016634:Radiosurgery / Q000009:adverse effects* / Q000295:instrumentation; D011879:Radiotherapy Dosage; D013739:Testosterone / Q000097:blood; D013972:Thyrotropin / Q000097:blood; D013974:Thyroxine / Q000097:blood; D016896:Treatment Outcome
D013739:Testosterone; D004958:Estradiol; D007334:Insulin-Like Growth Factor I; D011388:Prolactin; D005640:Follicle Stimulating Hormone; D013972:Thyrotropin; D013974:Thyroxine; D006854:Hydrocortisone