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While some tumor cells die quickly within the first few weeks after stereotactic radiosurgery, others may die more gradually over a period of 6 to 18 months or longer. Radiosurgery effectively stops the growth of the tumor or shrinks the size of the tumor; however, the tumor still remains present. Periodic follow-up MRIs will be required after treatment for the remainder of the patient's life to make sure the tumor does not resume growth.

Doses of radiation in the 1980s, when the technique of stereotactic radiosurgery was still in its infancy, were about 35 Gray or Gy (a unit used to measure radiation dose) but since the 1990s the doses have been reduced to between 14 and 17 Gy to minimize side effects while maintaining or improving maximum effectiveness. Continuing research focuses on reducing the radiation doses even further. A study was recently published from the University of Pittsburgh reporting success rates of 13 Gy for the treatment of acoustic neuromas.

Side effects of stereotactic radiosurgery are usually mild and may include:

• Nausea
• Neck stiffness
• Pain at the site of the screws used to attach the frame to the head
• Radiation injury - damage to tissue caused by exposure to radiation. This may develop 3-12 months after stereotactic radiosurgery and results in swelling of brain tissue. Resolution of the swelling is usually without treatment though some patients may require steroid treatment for persistent swelling.
• Some patients experience facial numbness and weakness or deafness on the side of treatment following radiosurgery which is usually temporary and typically occurs 6 to 18 months after treatment.

The cost of radiosurgery is 50% to 75% less than the cost of traditional acoustic neuroma microsurgery. It also involves a much shorter recovery time and some patients return to work the day after treatment.

Efficacy of Stereotactic Radiosurgery

Efficacy rates of stereotactic radiosurgery continue to improve due to:

• Improvement of MRI technology that allows tumors to be visualized earlier and in greater detail
• MRI allows for highly sophisticated treatment plans to deliver radiation to the tumor with pinpoint accuracy
• Improved technology has allowed for a reduction of the radiation dose needed for effective treatment

A study published in 2005 by investigators at the University of Pittsburgh involving 829 patients with acoustic neuromas who had been treated with stereotactic radiosurgery reported the following:

• Tumor control rates of 97% at 10 years
• Hearing preservation in 50-77% of patients
• 70% of tumors decreased in size at 10 years
• Less than 1% risk of facial neuropathy
• Less than 3% risk of trigeminal neuropathy
• All tumors which recurred were identified within the first three years of treatment
• Side effects occurred within the first 2 years following treatment

To read more about this study, please follow this link:

http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=Retrieve&db=pubmed&dopt=Abstract&listuids=15662809&queryhl=6&itool=pubmed_docsum

In 2005, the results of a study conducted in Japan were published regarding the outcome of 301 patients with acoustic neuroma who underwent Gamma knife radiosurgery. Patients were followed for an average of 7 years. Findings from this study included: