Role of gamma knife therapy in the management of pituitary tumors.

1. Gamma knife therapy is an effective method of delivering radiation to pituitary tumors that have failed surgery and may be used as primary treatment in circumstances in which the patient refuses or is unsuitable for a transsphenoidal procedure. 2. Stereotactic radiosurgery with the gamma knife unit is generally administered in a single session unlike fractionated radiotherapy, which is administered four to five times per week over a 6-week period. 3. Preliminary data suggest that resolution of pituitary hypersecretion is faster with gamma knife therapy than with conventional radiotherapy. 4. Because of the nature of the gamma knife therapy and the fact that the radiation dose conforms to the tumor shape, there is a steep fall-off of radiation to surrounding tissue. Accordingly, the radiation dose to extrapituitary brain is substantially less with gamma knife radiosurgery than with conventional radiotherapy. This suggests that the development of second brain tumors and neurocognitive complications, which are significant risks with conventional radiotherapy, is much less likely with gamma knife surgery. 5. Gamma knife radiosurgery can be used to ablate tumors invading the cavernous sinus. 6. Gamma knife radiosurgery is safe as long as the dose of radiation to the optic structures is kept under 10 Gy. 7. Long-term follow-up is required for pituitary tumors treated by gamma knife therapy so as to determine its efficacy as well as its effects on pituitary function and any resultant complications.