Hypopituitarism after Single-Fraction Pituitary Adenoma Radiosurgery: Dosimetric Analysis based on Patients treated Using Contemporary Techniques

Publication date: Available online 8 March 2018
Source:International Journal of Radiation Oncology*Biology*Physics
Author(s): Christopher S. Graffeo, Michael J. Link, Paul D. Brown, William F. Young, Bruce E. Pollock
PurposeHypopituitarism is the most frequent complication after pituitary adenoma radiosurgery (SRS). The dosimetric factors associated with pituitary insufficiency remain unclear despite more than 30 years of clinical usage.Methods and MaterialsRetrospective review of 97 patients having single-fraction SRS from 2007 until 2014. Eligible patients had no history of prior radiation, normal age- and gender-specific pituitary function before SRS, and at least 24 months of endocrine follow-up. Forty patients (41%) had hormone secreting tumors; 57 patients had non-secreting tumors (59%). The median prescription isodose volume was 2.8 cm³ (IQR, 1.3-4.7); the median tumor margin dose was 20 Gy (IQR, 15-25).ResultsThe median follow-up after SRS was 48 months (IQR, 34-68). Twenty-seven patients (28%) developed pituitary insufficiency at a median of 22 months (IQR, 12-36) after SRS. The rate of new endocrine deficits was 17% at 2-years (95% CI 10%-25%) and 31% at 5-years (95% CI 20%-42%). Male sex (HR=2.38, 95% CI 1.05-5.26, P=0.04), smaller pituitary gland volume (HR=0.99, 95% CI 0.99-0.99, P=0.01), and higher mean pituitary gland dose (HR=1.31, 95% CI 1.16-1.47, P<0.001) were associated with post-SRS hypopituitarism in multivariable analysis. The rate of hypopituitarism for patients with a mean gland dose <11.0 Gy at 2-years was 2% (95% CI 0%-4%) and 5-years was 5% (95% CI 0%-11%) whereas rate of hypopituitarism for patients with a mean gland dose ≥11.0 Gy at 2-years was 31% (95% CI 17%-43%) and at 5-years was 51% (95% CI 34%-65%).ConclusionsHypopituitarism after pituitary adenoma SRS increases in a time- and dose-dependent manner. Reducing the radiation exposure to the identifiable gland to a mean dose <11.0 Gy whenever feasible may lower the incidence of new hormonal deficits after pituitary adenoma SRS.



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