Gamma Knife Radiosurgery

John Han-Chih Chang, MD and Kenneth Blank, MD
Ultima Vez Modificado: 1 de noviembre del 2001

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Question
Dear OncoLink "Ask the Experts,"
My mother has brain cancer. She is retired and is 50 years old. In March of 1998 she had CT and MRI scans, which revealed a tumor in her brain stem. Then she had routine treatment, but it did not show a significant effect.

Experts in Nanjing, China suggested that she should be further treated with gamma knife radiosurgery. Then she was transferred to the center for gamma knife radiosurgery and prepared for the therapy.

In May of 1998, she had another MRI scan showing that the tumor had enlarged and was now also involving part of mesencephalon, pons and medulla oblongata. The tumor has almost invaded half of the brain stem.

The physician at the center of gamma knife radiosurgery recommended against gamma knife treatment at the present. He advised that she should have chemotherapy and radiotherapy first. If the tumor decreased in size, she could have gamma knife radiosurgery perhaps then.

My mother now feels very disappointed that she may never receive this advanced treatment. If you could offer help to us, please communicate with me quickly!


Answer
John Han-Chih Chang, MD and Kenneth Blank, MD, Editorial Assistants for Oncolink, respond:

Dear Anxious Son,
Thank you for your interest and question.

It seems to be a very difficult situation that your mother faces at this point. There seems to be extensive cancer involvement throughout the brain stem. Primary brain cancers are very difficult to treat and "cure." The mainstay of treatment is surgery and radiation therapy. Chemotherapy has been controversial as far as its effectiveness.

Your mother's care from the very limited information you have given, appears to be appropriate. The lesion that you describe could be treated with radiation therapy to a portion of her brain. This could be given at the same time, before or after the chemotherapy. Following this treatment, another MRI or CT scan could be done to assess the response. If the mass has reduced enough, perhaps stereotactic radiosurgery could be done with the gamma knife. The gamma knife can only effectively and safely treat masses that are 1 to 30 cubic centimeters in size. If it is any larger, one runs a significant increased risk of brain necrosis (focal death or destruction of normal brain cells) due to the volume of normal tissue included and the dose of radiation delivered. This is probably the reason that the physician advised performing the treatment now.

You mentioned that the gamma knife is advanced treatment. It is, in the sense that it is more technically sophisticated, but the data are not conclusive about it usefulness. It has not been seen to provide a survival advantage in most studies (ie University of Wisconsin, University of Florida, University of Arizona, etc.). There is current Radiation Therapy Oncology Group (RTOG 95-03) that is a phase III study comparing the effectiveness of using standard external beam radiation with or without radiosurgery (gamma knife). That study may bring us closer to the answer about radiosurgery's efficacy.

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