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Pituitary Adenoma...

From Medscape Neurology & Neurosurgery Conference Report

Key Reports From the 68th Annual Meeting of the Association of Neurological Surgeons
April 8-13, 2000
San Francisco, California

Gamma Knife for Pituitary Adenomas

Dr. Lawrence S. Chin, Assistant Professor of Neurosurgery at the University of Maryland Medical Center as well as Chief of Neuro-oncology and Director of the Gamma Knife Center in Baltimore, Maryland,[3] presented a retrospective review of 29 patients who had pituitary adenomas treated with the gamma knife. Endocrine evaluation revealed that 17 of the tumors were nonfunctional; however, 5 secreted prolactin, 4 secreted growth hormone, and 2 secreted adrenocorticotropic hormone. All patients received at least 1 gamma knife treatment with a mean peripheral dose of 12 Gy. To protect the optic chiasm, the gamma knife directed a lower mean dose of 7 Gy to this area. At follow-up, only 1 patient had regrowth of tumor, and none had an increase in hormone levels. There were no complications from this procedure.

Dr. Chin explained that most patients with pituitary tumors are initially treated with conventional neurosurgery, both to establish a tissue diagnosis, and to remove the tumor from the region of the optic nerve, which is more sensitive to radiation than other nearby cranial nerves. He noted that radiosurgery is "extremely effective in preventing recurrences" and that the gamma knife can "make that first surgery be the last surgery that these patients need."

According to Dr. Chin, there are approximately 50 gamma knife centers in the United States. Treatment can take place in an outpatient setting, with none of the usual risks, discomfort, or complications of conventional neurosurgery. Areas of potential improvement for gamma knife surgery include creating more sophisticated software to deliver radiation that conforms more to the tumor (in order to protect normal tissue) and developing new techniques for protecting the optic nerve, which would permit delivery of higher radiation doses. Improved imaging techniques will lead to more precise targeting of tumors. Dr. Chin expects to continue to follow his cohort of patients and repeat the analysis with other patients in 5 to10 years. "I'll be happy when we get 10-year and 20-year follow-up," he stated.

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