The role of gamma knife radiosurgery in the management of pituitary adenomas.

No treatment modality has been entirely successful in the management of pituitary adenomas. Although most patients with pituitary microadenomas can be cured by transsphenoidal surgery, the results are less satisfactory in macroadenomas in particular with suprasellar and/or parasellar extension. Additional treatment is then called for. Conventional fractional radiotherapy can often control tumour growth but is limited to 45-50 Gy with a very slow reduction in elevated pituitary hormones and a high incidence of pituitary insufficiency. Stereotactic radiosurgery allows the delivery of radiation with high precision to the target with low doses to the surrounding tissues permitting higher radiation doses. Gamma knife radiosurgery using photon energy with gamma beams from multiple cobalt 60 radiation sources is now used in many centers. It can be carried out in an outpatient setting with one single treatment. A more rapid normalization of pituitary hormone hypersecretion than with conventional radiation can be achieved as well as arrest of tumour growth and reduction of tumour mass. We therefore consider gamma knife radiosurgery as a valuable compliment to pituitary surgery. Long-term prospective studies are needed to evaluate the frequency of pituitary insufficiency in patients where the target area is determined with stereotactic magnetic resonance imaging (MRI).