- To prevent progression of aggressive tumours after an incomplete surgical resection.
- To treat hormonally active tumours (e.g., acromegaly or Cushing’s) that failed to respond to surgical and medical therapy.
There are two main modalities of radiation:
Fractionated radiotherpy. The radiation dose is divided over time (fractions), typically in daily doses over 4-6 weeks, requiring daily treatment visits. Radiation is given to a field which includes both the tumour but also some surrounding healthy tissue, such as the normal pituitary gland.
Radiosurgery (e.g., γ-knife radiosurgery). Using imaging guidance (stereotactics), a radiation beam can be more targeted at the lesion. This makes it possible to maximizes the radiation dose given to the lesion and minimizes the radiation exposure of the surrounding healthy tissue. The treatment is given in a single dose, requiring a single treatment visit. It is appropriate for lesions that are well-demarcated and not too close to the optic apparatus.
Targeted radiation with radio-labeled ligands is under investigation.
Hypopituitarism. Can be delayed, especially in fractionated radiotherapy.
Secondary brain tumours. 2% at 10 years, 2.4% at 20 years in fractionated radiotherapy. Appears to be much lower in γ-knife radiosurgery.
Di Ieva A, Rotondo F, Syro LV, Cusimano MD, Kovacs K. Aggressive pituitary adenomas–diagnosis and emerging treatments. Nat Rev Endocrinol. 2014 Jul;10(7):423-35.
Castinetti F, Régis J, Dufour H, Brue T. Role of stereotactic radiosurgery in the management of pituitary adenomas. Nat Rev Endocrinol. 2010 Apr;6(4):214-23.
Rowe J, Grainger A, Walton L, Silcocks P, Radatz M, Kemeny A. Risk of malignancy after gamma knife stereotactic radiosurgery. Neurosurgery. 2007 Jan;60(1):60-5; discussion 65-6.