Fractionated radiotherapy (RT) is effective in achieving disease control and normalisation of hormone levels. While overall safe, it is not devoid of side effects and should only be employed when the risks from the disease are considered to outweigh the risks from treatment. Currently RT tends to be withheld until progression unless there is a threat to function, particularly vision, from progressive tumour. RT is recommended for patients with secreting adenoma not achieving biochemical cure following surgery and medical treatment. Normalisation takes months to years and the delay is related to pre-treatment hormone levels.
Modern developments in radiotherapy aim to treat less normal tissue to significant radiation doses minimising the risk of late normal tissue injury. Treatment can be given as fractionated (fractionated stereotactic radiotherapy fSRT/SCRT) or single fraction treatment (stereotactic radiosurgery SRS) and relies on increased accuracy of tumour delineation with MRI. While there is perception that it is the use of modern technology which determines the outcome, the success is more likely related to operator skill and expertise and the accuracy in identifying the tumour.
Conventional fractionated RT achieves tumour control in 9095% of patients at 10 and 8590% at 20 years. Published results of fSRT show similar early results but have not reached the maturity of long term results of conventional RT. SRS, while apparently more convenient, is less effective in achieving tumour control without faster decline in hormone levels in secreting tumours. SRS of larger adenomas close to critical structures carries a significant risk of radiation damage. Fractionated irradiation either as modern conformal or fractionated stereotactic RT remains the standard of care with SRS considered as an experimental and in some instances less effective treatment.