Brain metastasis from an unknown primary
The last thing I’d like to just mention about, and it’s an important point, is the issue of brain metastasis from an unknown primary.If one looks at a series from M.D. Anderson, 220 patients with brain metastasis. Approximately 39 of those patients, or 18%, were without a known systemic site. The median age of these patients is approximately 55. Most of them had good performance status. About half of those lesions were multiple, however half of them were single. One actually looked at the histology of those tumors.
Approximately 31% were adenocarcinomas, representing by far the greatest number. In the few patients where a primary was eventually found, usually at autopsy, lung represented the most common primary site. The important thing to know about these tumors however is that there is a subset of these patients who can actually do quite well. All these patients were treated with whole brain radiation, 30 gray, and that intracranial disease-free survival at five years was 72% of these patients. And that the overall median survival of these patients was well over a year, whereas 12% of these patients surviving eight years and probably effectively cured of their disease.
What this says is that, particularly if you have a young middle aged person, good performance status, who has a solitary metastasis with no known primary, that that patient should indeed be treated very aggressively, both with surgery and radiation. Because that patient has a very good chance of having a long term disease-free survival, and potentially even cured.