Radiation therapy is usually reserved for people who have some tumor remaining after surgery and do not respond to medications. Because radiation leads to a slow lowering of GH and IGF-I levels, these patients often also receive medication to lower hormone levels. The full effect of this therapy may not occur for many years.
The two types of radiation delivery are conventional and stereotactic. Conventional radiation delivery targets the tumor with external beams but can damage surrounding tissue. The treatment delivers small doses of radiation multiple times over 4 to 6 weeks, giving normal tissue time to heal between treatments.
Stereotactic delivery allows precise targeting of a high-dose beam of radiation at the tumor from varying angles. The patient must wear a rigid head frame to keep the head still. The types of stereotactic radiation delivery currently available are proton beam, linear accelerator (LINAC), and gamma knife. With stereotactic delivery, the tumor must be at least 5 mm from the optic chiasm to prevent radiation damage. This treatment can sometimes be done in a single session, reducing the risk of damage to surrounding tissue.
All forms of radiation therapy cause a gradual decline in production of other pituitary hormones over time, resulting in the need for hormone replacement in most patients. Radiation also can impair a patient's fertility. Vision loss and brain injury are rare complications. Rarely, secondary tumors can develop many years later in areas that were in the path of the radiation beam.
Center for Image-Guided Neurosurgery
Gamma Knife surgery represents one of the most advanced means available to manage brain tumors; arteriovenous malformations and pain or movement disorders. The procedure is unique because, with the Gamma Knife, no surgical incision is performed to expose the target.
The Gamma Knife can destroy deep-seated blood vessel malformations in the head and brain tumors once considered inoperable. It can also eliminate pain conditions and certain movement disorders, as well as silence malfunctioning areas of the brain precisely, to stop seizures or ease disabling pain problems that have not responded to other management strategies.
The Center for Image-Guided Neurosurgery at the University of Pittsburgh Medical Center installed the first North American Gamma Knife in 1987 and subsequently introduced and pioneered each succeeding generation of technological improvement. Staffed by a highly skilled and productive team, we seek to provide rapid screening, scheduling, and completion of Gamma Knife radiosurgical procedures.
During UPMC's first 20 years of experience, more than 8,500 patients have undergone radiosurgery in the department's Gamma Knife units. In May of 2004 our center added a third Gamma Knife unit, becoming the only center in the world with three operating units. In September of 2007, the new Perfexion® Gamma Knife unit -- encompassing the latest advances in radiosurgical technology -- was installed.
The Gamma Knife Unit
The Gamma Knife contains up to 201 cobalt-60 sources of approximately 30 curies each, placed in a circular array in a heavily shielded unit. The unit directs gamma radiation to a target point. Such target points selected in the brain can be placed at the center of the radiation focus, allowing a tumoricidal radiation dosage to be delivered in one treatment session. The Gamma Knife has proved effective for thousands of patients with benign or malignant brain tumors, vascular malformations, pain or other functional problems.