New techniques aim to reduce cognitive side effects of whole brain radiation

Radiation therapy for brain tumors, particularly whole-brain radiotherapy (WBRT), is often avoided by patients due to its many side effects. One of the most concerning side effects reported by cancer patients is cognitive decline.

Won Yong-gyun, a professor of radiation oncology at Soonchunhyang University Cheonan Hospital, discussed the treatment of lung cancer patients with brain metastases in a YouTube session hosted by the Korean Society for Lung Cancer. He pointed out that “cognitive decline, a symptom similar to dementia, is a common side effect of WBRT.”

So, what kind of cognitive decline occurs when patients with brain tumors—whether primary or metastatic from lung, breast, or other cancers—undergo WBRT? “Patients may experience memory loss, reduced learning ability, and slower calculation skills,” said Professor Won.

However, not all patients who receive WBRT experience cognitive decline. “It’s not a universal side effect,” he explained. “If symptoms are expected to worsen significantly without treatment, we recommend WBRT despite its risks.”

New radiation techniques have been developed to reduce the risk of cognitive impairment. “One method is intensity-modulated radiation therapy (IMRT), which allows for reduced radiation to memory-related areas of the brain such as the hippocampus and amygdala,” Professor Won noted. This adjusted WBRT method is now being used in select cases.

In conventional WBRT, the same radiation dose is delivered to the entire brain, resulting in a uniform image on scans. In contrast, IMRT produces scans with varying colors, reflecting the adjusted doses to different brain regions. “The areas with less color represent parts like the hippocampus and amygdala, where we've intentionally reduced the radiation,” said Professor Won. “It’s an attempt to mitigate cognitive decline.”

Interestingly, the most common side effect of WBRT isn’t cognitive decline—it’s hair loss. “Unlike radiation to other parts of the body, brain radiation causes complete hair loss, and it typically takes two to three months for hair to begin growing back,” he said.

Stereotactic radiosurgery methods like CyberKnife and Gamma Knife, which are often used to reduce WBRT side effects, can also cause hair loss. “If the treatment area is close to the skull, localized hair loss around the site can occur,” Professor Won explained.

Aside from hair loss, other common WBRT side effects include headaches, nausea, and fatigue. “Fatigue is especially concerning in elderly patients, as it can significantly reduce their overall physical functioning,” he said. “It’s always a challenge to decide whether WBRT is appropriate for older patients.”

Because of these concerns, specific criteria are used to determine whether WBRT should be administered. “It is generally recommended when the number of brain metastases is too high or when the metastases are expected to cover the entire brain,” said Professor Won. “Factors such as cancer type, life expectancy, and patient age are also considered when choosing a treatment plan.”