Endocrine Abstracts (2019) 65 P293 | DOI: 10.1530/endoabs.65.P293

Frequency and timing of hypopituitarism as a consequence of pituitary directed radiotherapy; a retrospective cohort study

Ryan Goindoo1, Furhana Hussein1, Haval Surchi1, Sonali Gunatilake1, Jose Ortez-Toro1, Simon Cudlip2, Claire Hobbs3, Bahram Jafar-Mohammadi1 & Aparna Pal1

1OCDEM, Oxford University Hospital, Oxford, UK; 2Neurosurgery Oxford University Hospital, Oxford, UK; 3Oncology Oxford University Hospital, Oxford, UK

Background: Patients receiving radiotherapy for residual or recurrent pituitary adenoma require regular surveillance for the development of anterior pituitary axis deficit. Whilst the sequelae of hypopituitarism post cranial irradiation is well recognized, there are relatively varied incidences of new onset hypopituitarism post-conventional radiotherapy, reported in the literature. We aimed to investigate timing and frequency of the individual axis deficits in adults who have received pituitary targeted radiotherapy in our centre.

Objective/aim: To determine the rates and timing of deficit in the individual anterior pituitary hormone axes post pituitary radiotherapy.

Methods: We performed a single-centre retrospective analysis of patients receiving pituitary radiotherapy for recurrent or residual pituitary adenoma between 1995 and 2019. Eligible patients had no history of prior radiation, normal pituitary function prior to radiotherapy and at least 12 months of endocrine follow-up. We assessed the effects of pituitary radiotherapy upon endocrine function in 74 adults (44 males) receiving a dose of 45 Gy in 25 fractions for recurrent/residual pituitary adenoma.

Results: Mean age at the time of receiving RT was 53 years and the median duration of endocrine follow up was 9.1 years. Overall prevalence of radiotherapy induced hypopituitarism was 26.7%. GH, FSH/LH, TSH and ACTH deficiency were present in 24.4%, 22.2%, 20% and 22.2% of patients respectively at a median time of 8.3 years, 10.8 years, 9.3 years and 9.3 years respectively. Rate of new axis deficit was 8% at 2 years, 20% at 5 years and 27% at 10 years.

Conclusion: Our data reiterate the need for lifelong endocrine follow-up of patients receiving pituitary radiotherapy with 15% patients developing new axis deficit at >10 years post RT. Knowledge of frequency and timing of pituitary deficit is important when counselling patients regarding the potential risks of radiotherapy. Further analysis of new radiation techniques and long-term hypothalamic−pituitary dysfunction is needed.