Endocrine Abstracts (2018) 59 N1.2 | DOI: 10.1530/endoabs.59.N1.2

The role of gamma knife in the management of pituitary adenomas

John Newell Price

University of Sheffield, Sheffield, UK.

Pituitary radiotherapy plays an important role in the overall management of pituitary disease, but needs discussion at an expert regional pituitary MDT. Repeat surgical exploration is increasingly performed either as an alternative to radiotherapy or to further reduce tumour bulk ahead of radiotherapy. Careful discussion with the patient on the risks and benefits of radiotherapy, and all the other options, is essential. It is best to consider the control of tumour growth and any hormonal hypersecretion separately – use of radiotherapy to control an expanding tumour in one patient with no hypersecretion, or in a patient with a tiny tumour volume but in whom there is excess hormone secretion and for whom other medical therapies may be used. If there is pre-existing hypopituitarism there is ‘less to loose’ by radiotherapy, but even when pituitary function is intact it is essential to control tumour growth. The choice between the different modalities of radiotherapy is governed primarily by the anatomy of the tumour target. Modern fractionated radiotherapy over 5–6 weeks is highly conformal to the tumour target but the gamma knife offers single dose radiotherapy to the tumour volume (targeting accuracy 0.2 mm) with minimal radiation to surrounding structures. The main limiter to the use if the gamma knife is the distance to the optic apparatus so that dose is kept to <8Gy to that structure. Although it is commonly thought that gamma knife has a lower risk of late onset hypopituitarism our experience at the National Centre for Stereotactic Radiosurgery in Sheffield in over 340 patients (125 with acromegaly) is that the rates are not dissimilar to fractionated radiotherapy, but it is highly effective for control of hormonal hypersecretion and our 30 y follow data indicate no evidence of increased risk of other long term CNS sequelae, such as stroke.

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