Effect of Treatment Modality on the Hypothalamic–Pituitary Function of Patients Treated with Radiation Therapy for Pituitary Adenomas: Hypothalamic Dose and Endocrine Outcomes

Abstract

Background: Both fractionated external beam radiotherapy and single fraction radiosurgery for pituitary adenomas are associated with the risk of hypothalamic–pituitary (HP) axis dysfunction.Objective: To analyze the effect of treatment modality (Linac, TomoTherapy, or gamma knife) on hypothalamic dose and correlate these with HP-axis deficits after radiotherapy.Methods: Radiation plans of patients treated post-operatively for pituitary adenomas using Linac-based 3D-conformal radiotherapy (CRT) (n = 11), TomoTherapy-based intensity modulated radiation therapy (IMRT) (n = 10), or gamma knife stereotactic radiosurgery (n = 12) were retrospectively reviewed. Dose to the hypothalamus was analyzed and post-radiotherapy hormone function including growth hormone, thyroid stimulating hormone, adrenocorticotropic hormone, prolactin, and gonadotropins (follicle stimulating hormone/luteinizing hormone) were assessed.Results: Post-radiation, 13 of 27 (48%) patients eligible for analysis developed at least one new hormone deficit, of which 8 of 11 (72%) occurred in the Linac group, 4 of 8 (50%) occurred in the TomoTherapy group, and 1 of 8 (12.5%) occurred in the gamma knife group. Compared with fractionated techniques, gamma knife showed improved hypothalamic sparing for DMax Hypo and V12Gy. For fractionated modalities, TomoTherapy showed improved dosimetric characteristics over Linac-based treatment with hypothalamic DMean (44.8 vs. 26.8 Gy p = 0.02), DMax (49.8 vs. 39.1 Gy p = 0.04), and V12Gy (100 vs. 76% p = 0.004).Conclusion: Maximal dosimetric avoidance of the hypothalamus was achieved using gamma knife-based radiosurgery followed by TomoTherapy-based IMRT, and Linac-based 3D conformal radiation therapy, respectively.

The EPTN consensus-based atlas for CT- and MR-based contouring in neuro-oncology

“…Since the lateral border is not clearly visible, the contour was bounded laterally 3 mm from the third ventricle. Delineation on a T1 weighted MR is strongly recommended [13][14][15][16].…”

The Feasibility of Sparing the Hippocampus and Hypothalamic -Hypophysial Axis During Whole Brain Radiotherapy: A Dosimetric Study

“…The hypothalamus was delineated by utilizing the method described by Elson et al 27 and additional MRI atlases. 28 In brief, the most cranial contouring section corresponded to the anterior commissure, which is located at the medial sides of the third ventricle ( Figure 1).…”

Hypopituitarism after gamma knife radiosurgery for pituitary adenoma

“…Hypopituitarism is the most prevalent complication of GKRS [3]. The reported incidence of pituitary insufficiency is highly heterogeneous across studies and it ranges between 11.6 and 39% depending mainly on the duration of follow-up [7,9,23,24]. For example, the study with one of the longest follow-up periods published by Gopalan et al [7] reported the greatest incidence of new pituitary deficits after GKRS for non-functioning pituitary adenoma (39%).…”

“…Hypopituitarism is one of the most common complications of GKRS. The data on its incidence and possible prognostic/risk factors are rather variable among studies [3][4][5][6][7][8][9][10][11] and highly dependent on the definition of endocrine dysfunction that has been used [12][13][14][15]. The incidence of hypopituitarism also depends on several factors, such as the type and extent of surgery prior to GKRS, duration of follow-up, tumor volume, tumor function, prescription dose of radiation and preexisting pituitary function [4,16].…”