Endocrine Abstracts

Introduction: Fractionated stereotactic radiotherapy (FSRT) is used in the treatment of surgically inaccessible meningiomas, primarily in the base of the skull. Development of hypopituitarism following FSRT is inexhaustively investigated. We aimed to elucidate the cause of hypopituitarism in patients treated with FSRT for benign meningiomas of the anterior skull base.

Methods: All patients undergoing FSRT for benign meningioma of the skull base between July 2003 and June 2009 were included in the study. Patients baseline was established before FSRT and they were then followed with regular neuroendocrinological testing. Tumour control was monitored at neurosurgical follow-up every 2 years using MRI. Pituitary radiation dose was calculated using the dose-volume histogram for the pituitary gland generated by the radiation planning program.

Results: A 31 patients were included in the study. Median follow up was 5.2 years (range 2.2–7.8). Ten patients developed one or more new pituitary hormone deficits. Five years after FSRT, 70–79% of patients retained sufficient hormone function in each axis included in the study. Tumour control (defined as either a stable or regressing tumour) was obtained in 81% of cases. Median biological effective dose to the pituitary gland was 83 Gy (range 32–92). Multiple linear regression analysis showed that there was a statistically significant relationship between i) failure of tumour control (P=0.0005), ii) tumour in the pituitary sella (P<0.0001) and iii) time from FSRT to latest follow-up (P=0.0116) and the number of affected pituitary axes.

Conclusion: Our results show a significant relationship between mass effects of the tumour and pituitary axis failure as well as a significant time component in the development of hypopituitarism in these patients. It is possible that the findings of this study can explain pituitary axis failure in patients treated with radiation therapy for pituitary adenoma and craniopharyngeoma.