Researchers evaluate efficacy of GKRS in patients with pituitary adenoma

In 2009, it was estimated that a total of 22,070 new cases of brain and other CNS tumors were diagnosed. Pituitary adenomas represent one of the most common brain tumors. Large studies report that approximately 10-20 percent of the population harbors a pituitary tumor. According to the Central Brain Tumor Registry of the United States, 13.4 percent of all brain and CNS tumors diagnosed in 2009 were located in the pituitary. Although surgical resection and medical management can be used to treat certain types of pituitary tumors, recurrent or residual tumors are not uncommon and frequently require treatment with stereotactic radiosurgery.

Swedish physician and professor of neurosurgery at the Karolinska Institute in Stockholm, Lars Leksell treated the first pituitary adenoma patient with the Gamma Knife® in 1968. Since then, Gamma Knife radiosurgery (GKRS) has been used to treat thousands of patients with a recurrent or residual pituitary adenoma. Many single center, retrospective studies have documented its efficacy. Unfortunately, most reports consist of fewer than 100 patients, making statistical analysis of such small groups problematic.

Researchers at the University of Virginia Health Science Center in Charlottesville, Va. and Brigham and Women's Hospital in Boston, evaluated the efficacy of GKRS in a total of 418 radiosurgery patients. The results of this study, Gamma Knife Radiosurgery for Pituitary Adenomas: Factors Related to Radiologic and Endocrine Outcomes in a Series of 400+ Patients, will be presented by Jason P. Sheehan, MD, PhD, 5:01 to 5:15 pm, Monday, May 3, 2010, during the 78th Annual Meeting of the American Association of Neurological Surgeons in Philadelphia. Co-authors are Nader Pouratian, MD, PhD, Edward R. Laws Jr., MD, and Mary Lee Vance, MD. Dr. Sheehan will be presented with the Synthes Skull Base Award for this research.

The current study evaluates the largest group of radiosurgery patients with a pituitary adenoma, to date, analyzing factors related to endocrine remission, control of tumor growth, and development of pituitary deficiency. Included in this study were patients with a minimum follow-up of 6 months (median 31 months). Statistical analysis was performed to evaluate for significant factors (p<0.05) related to treatment outcomes. The following results were noted:

•In 90.3 percent of patients, there was tumor control (i.e. no growth or tumor shrinkage). A higher radiation dose significantly resulted in tumor shrinkage.

•In patients with a secretory (i.e. functioning) pituitary adenoma such as in Cushing's disease or acromegaly, the median time to endocrine remission was 48.9 months. A higher radiation dose correlated with a faster time to endocrine remission.

•Smaller adenoma size correlated with improved endocrine response in those patients with secretory adenomas. Temporarily halting pituitary suppressive medications at the time of radiosurgery led to an improvement in endocrine response.

•New onset of a pituitary hormone deficiency following radiosurgery was seen in 24.4 percent of patients. These patients were placed on hormone supplementation as required. The two most common hormone deficiencies following radiosurgery were thyroid and growth hormone.

"Smaller tumor size improves the chances of endocrine control and lowers the risk of new pituitary hormone deficiency following stereotatic radiosurgery. A higher radiosurgical dose offers a greater chance of endocrine and tumor control," remarked Dr. Sheehan.

"Radiosurgery is an excellent treatment option for patients with recurrent or residual pituitary tumors. It offers a high rate of tumor and endocrine control. As such, it allows most patients to avoid repeat open surgery or lifelong, expensive medical management," concluded Dr. Sheehan.