Is an increase in CA 125 in breast cancer patients an indicator of pleural metastases?

The retrospective analysis of 250 breast cancer patients with disseminated disease provided evidence that the increase in CA 125 serum levels in these patients was caused by lung metastases or pleural effusions. Seven patients with lung metastases and pleural involvement had elevated CA 125 levels, while in four patients with lung metastases but without pleural effusions CA 125 levels remained normal. In patients with only bone or liver metastases CA 125 levels were usually not elevated. If these results are confirmed, CA 125 would be the first tumour marker in breast cancer whose levels could be associated with one single site of metastases.