Ovarian Cancer: CA 125 is rising but PET scans are clear.

4.5 years of Stage 3 high grade serous ovarian. I’m 82. My sixth chemo is now monthly single agent Carboplatin which reduced tumor burden greatly with clear PET scans but CA 125 which started at 1500 a year ago when I began the Carboplatin then was in normal range and is now 110. Last PET still clear and feeling well. Taking Procrit for Anemia. About to have a third PET scan in 6 months to see if Carbo is still working. I tolerate it well and hope I don’t need a new Chemo since with CKD we’re running out of options. Could the Carbo still be working some but just not as well? Others experiences are welcome.