Low-dose radiosurgery of non-functioning pituitary adenomas

Amr El-Shehaby, MD1, Wael Reda, MD1, Khaled Abdel Karim2, Sameh Roshdy, MSc3

1Gamma Knife Center Cairo, Nasser Institute 2Gamma Knife Center Cairo 3Gamme Knife Center Cairo, Nasser Institute

Keywords: pituitary adenoma, radiosurgery, gamma knife, outcome, vision

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     The main concerns when performing GKS (Gamma knife radiosurgery) for pituitary adenoma is visual and pituitary function preservation while achieving tumor growth control. Higher prescription doses are typically correlated with a higher incidence of postradiosurgical hormonal deficiencies.
     The goal of the study was to retrospectively analyze the feasibility of using a lower prescription dose in the treatment of non-functioning pituitary adenomas and its effect on vision, pituitary function and growth control.
     The study was carried out on 38 patients with non-functioning pituitary adenomas treated between January 2002 and July 2008. Twenty one patients were available for follow up for at least 2 years (13 males and 8 females). Nineteen patients were previously operated. Three cases developed pituitary dysfunction after surgery. One patient had an abnormal pituitary hormone profile before radiosurgery due to an attack of pituitary apoplexy. Visual field defects were present in 12 patients.
     The prescription dose was 12 Gy in all patients. The tumor volume ranged from 0.5 to 11.8 cc (mean 4.8 cc). The maximum dose to the visual pathway was kept below 10 Gy. The mean maximum dose to the visual pathway was 7.9 Gy.
     The patients were followed up for a period of 24 to 90 months (mean 44 months). The tumor size decreased in 11 (52%) patients and remained stable in 9 (43%) patients. In one patient there was tumor growth outside the previous radiation field (on the contralateral side). Of the 12 patients with visual field defects, 9 (75%) experienced an improvement and the rest remained stable. In only four patients was the visual improvement associated with tumor shrinkage. The hormonal profile remained normal in all except the 4 patients with preradiosurgical pituitary dysfunction.
     This was a retrospective study.
     The 12 Gy prescription dose used in this study seems to be sufficient at producing tumor control sparing the patient from radiation-induced pituitary dysfunction. This is even supported by the visual improvement reported in a number of cases.
     A larger series and longer follow up is required to confirm the outcome of 12 Gy radiosurgery for pituitary tumors.


Project Roles:

A. El-Shehaby (), W. Reda (), K. Karim (), S. Roshdy ()