Avoiding Damage to Neurocognitive Regions of the Brain During Cranial Radiation

Radiation oncologists are trying to find ways to avoid damage to the critically important hippocampus and limbic circuit of the brain when cranial radiation is required to treat existing or potential metastatic tumors. The goal is to spare these areas, which are responsible for short-term memory, as well as emotions, motivation, and a variety of executive functions, such as decision-making and planning.

Cranial radiation is used to destroy tumors that have spread to the brain, which occurs in 20% to 25% of all cancer patients. It is also used prophylactically to prevent the development of overt intracranial metastases in patients diagnosed with small-cell lung carcinoma.

But there is a flipside to the treatment. Because the hippocampus and the limbic area are irradiated along with the rest of the brain, the treatment frequently causes memory lapses, difficulty with executive planning, and poor fine motor control. The consequences can be devastating for patients, whose quality of life is deeply affected.

In a review of records for 107 patients with 700 lesions, the team of radiation oncologists at Rush University Medical Center (Chicago, IL, USA) found that metastases had occurred in the hippocampus in only 0.8% of the cases, and in the limbic circuit in fewer than 3% of cases. That finding encouraged them to determine whether it might be possible to deliver cranial radiation to the brain, but not to these specific areas--eliminating metastases or potential metastases with radiation but sparing the hippocampus and the limbic areas, where metastases were unlikely to occur.

In their feasibility study, the researchers were able to demonstrate that the hippocampus and limbic circuit can be largely spared using sophisticated equipment that targets the radiation to specific areas. The study's results were presented at the annual meeting of the American Society for Radiation Oncology, which is being held November 1-5, 2009, in Chicago, IL, USA. "We have shown that it is possible to reduce the dose of radiation to this area, while treating the rest of the brain, where the cancer is located, at full dose,” said Dr. Arnold Herskovic, principal investigator of the study.

The study was performed using a TomoTherapy (Madison, WI, USA) Hi-Art system, which enables the treatment of tumors with image-guided radiation therapy. The researchers expect to start a clinical trial of the new procedure soon to determine whether in fact it can both prevent or treat brain metastases and minimize long-term neurocognitive consequences.

Related Links:
Rush University Medical Center
TomoTherapy