The FDA grants accelerated approval to the oral chemotherapy drug temozolomide (Temodar) to treat anaplastic astrocytoma (a form of high-grade glioma) that recurs following other therapy. The approval is based on early-stage data suggesting that the drug shrinks tumors and is generally well tolerated. In 2005, temozolomide receives full approval for this and other high-grade gliomas, based on data showing that adding the drug to initial radiation therapy increases two-year survival by as much as 50 percent.

After nearly two decades of research, doctors begin using a non-invasive technique known as Gamma Knife to treat certain brain tumors. Also called stereotactic radiosurgery, the approach utilizes precisely focused radiation waves to disrupt cancer cell function and replication, while leaving the brain tissue surrounding the tumor largely untouched. Gamma Knife may also be combined with other forms of cancer therapy, including surgery. The approach continues to be refined today.

Radiation therapy becomes a mainstay of treatment for glioblastoma, a highly aggressive form of glioma, based on data showing it extends median survival from 3 months to about 9 months. This is the first time a treatment is proven effective against any brain cancer. Today, radiotherapy is used alone or with chemotherapy, both before and after surgery, and in patients with inoperable tumors.

Researchers perform the first computed tomography (CT) scan on a human patient – a woman with a suspected brain tumor. With CT scanning, which uses X-rays to create images of "slices" of the brain, doctors are for the first time able to clearly see tumors arising in the soft tissue of the brain. Over the following decades, this technology continues to be refined and used in combination with other imaging approaches, such as MRI.