This research study is being conducted to evaluate a structured monitoring approach, called active surveillance, for people with brain metastases who are being treated with cancer medicines instead of radiation therapy. Brain metastases occur when cancer spreads to the brain and can cause serious symptoms if not carefully managed.

In the past, radiation therapy was almost always required to treat brain metastases because standard cancer medicines did not work well in the brain. While radiation therapy can be very effective, it may also cause significant side effects that affect memory, thinking, and quality of life. More recently, newer cancer medicines have been developed that are able to reach the brain and control brain metastases without the immediate need for radiation therapy.

The purpose of this research study is to find out whether it is safe and practical to closely monitor patients receiving these cancer medicines using a planned schedule of follow-up visits and brain imaging. Researchers will evaluate whether this monitoring approach can reliably track tumor changes in the brain and identify when additional treatment, such as radiation therapy, may be needed.

This study is important because there is currently no standard method for monitoring patients with brain metastases who are treated with systemic (whole-body) cancer therapy alone. The information gathered from this pilot study may help develop safer and more effective care strategies for future patients who may be able to delay or avoid radiation therapy.