Welcome, @ampeltekian. You'll notice that I moved your post about the tumor marker CA 15-3 to this existing discussion in the Breast Cancer group.
- CA 15-3 cancer tumor marker: https://connect.mayoclinic.org/discussion/ca-15-3-cancer-tumor-marker/

CA15-3 levels can be higher than normal with cancerous and non-cancerous conditions. I know this information can cause great anxiety. The wait for a PET scan is really hard. Members like @rraw @leeann66 @auntieoakley know this all too well and are here to support you through the wait.

I notice that you also ask "Is metastatic cancer treatable?" and "Does breast cancer spread to the bones in the absence of a tumor in the breast?"

Yes, there are treatments to manage metastatic breast cancer. It sounds like you have not yet received a confirmation that you have cancer. Have you had a mammogram or other imaging testing done to confirm that there is no lump?