Radiation oncologists at Rush University Medical Center are intent on finding 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 cancers.
The goal is to spare these areas, which are responsible for short-term memory, as well as emotions, motivation, and a range of executive functions, such as planning and decision-making.
Cranial radiation is used to destroy tumors that have spread to the brain, which happens in 20 to 25 percent 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 downside to the treatment. Because the hippocampus and the limbic area are irradiated along with the rest of the brain, the treatment often 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 found that metastases had occurred in the hippocampus in only 0.8 percent of the cases, and in the limbic circuit in fewer than 3 percent of cases.
That finding emboldened them to determine whether it might be possible to deliver cranial radiation to the brain, but not to these particular areas - eliminating metastases or potential metastases with radiation but sparing the hippocampus and the limbic areas, where metastases were unlikely to occur.