What is the best approach in a patient with a single brain metastasis in the setting of progressing systemic disease?

There is no single "best approach" for a single brain metastasis, even in the setting of progressing systemic disease.

First, ask if it is obvious that a single lesion is a brain metastasis. The patient needs to be made aware that the diagnostic error rate can be as high as 15%.

If unsure, then tiss...