Effects of gamma knife radiosurgery of pituitary adenomas on pituitary function

Abstract

Object. The authors undertook a retrospective analysis of the incidence and time course of pituitary insufficiency following gamma knife radiosurgery (GKS) for pituitary adenomas. Methods. Pituitary adenomas in 92 patients were analyzed. There were 61 hormonally inactive tumors, 18 prolactinomas, and nine somatotropic and four adrenocorticotropic adenomas. The mean tumor volume was 3.8 cm3 (range 0.2–14.6 cm3). The mean prescription dose was 15 Gy. The mean prescription isodose was 50.7%. The mean follow-up time was 4.6 years (range 1.2–10 years). The following new or deteriorating insufficiencies that did not require treatment were recorded for the different pituitary axes: follicle-stimulating hormone (FSH)/luteinizing hormone (LH) 19 (20.6%), thyroid-stimulating hormone (TSH) 32 (34.8%), adenocorticotropic hormone (ACTH) 10 (10.9%), and growth hormone (GH) 26 (28.3%). For new insufficiencies or deterioration requiring replacement therapy, the figures were as follows: FSH/LH 20 (21.7%), TSH 22 (23.9%), ACTH eight (8.7%), and GH 12 (13%). Spot dosimetry was performed in 59 patients in the hypothalamic region, the pituitary gland, and pituitary stalk. The pituitary stalks in patients with deterioration of pituitary function received a statistically higher dosage of radiation, 7.7 ± 3.7 Gy compared with 5.5 ± 3 Gy (p = 0.03). Conclusions. The function of the residual normal pituitary gland is less affected following GKS of pituitary adenomas than after fractionated radiotherapy. Nonetheless, increased attention needs to be exercised to reduce the dose to the stalk and pituitary gland to minimize the incidence of these complications.

LINAC-radiosurgery for nonsecreting pituitary adenomas

“…This is reasonably consistent with the results of three GKRS series [15,23,47]. Vladyka et al [47] found a mean dose of more than 17 Gy and 20 Gy to be a risk factor for impairment of the gonadotrophic and corticotrophic/thyrotrophic function, respectively.…”

Radiation therapy in acromegaly

“…Overall, local control of tumor growth is similar between fractionated and single fraction radiation therapy with rates of approximately 95% at 5 years, similar to nonfunctioning adenomas [4,19]. In contrast, stereotactic radiosurgery appears to produce a faster hormonal ablative response than fractionated radiation [3,8,20].…”

Long-Term Follow-up of Patients with Pituitary Macroadenomas after Postoperative Radiation Therapy

“…Linac-based stereotactic radiotherapy and radiosurgery as well as gamma knife radiosurgery have emerged as treatment options, and the results achieved by those techniques are encouraging [7,11,24,27,28,35,36]. Whether late side effects (e.g., hypopituitarism) following stereotactic techniques are less frequent than after conventional external-beam radiotherapy has not yet been shown, since most follow-up data are still limited [5,8,14,18,20,23,29].…”