Confused - CA125 increased after debulking

First, I'd like to say how much help this group has already been and thank you!

 

My Mom, a young 71, was diagnosed with peritoneal cancer last month (Nov. 2012).  Her CA125 was 5,338 November 24, 2012.  The doctor first suspected ovarian cancer, but after surgery to remove as much of the cancer has possible, he said the ovaries were only minimally affected and that it presented itself to be peritoneal cancer.

 

The doctor said he was able to removed 95% of the cancer, but explained the remaining cancer was like paint splatter.  There is cancer on the outer surface of all of her abdonial organs, but he said it hadn't invaded any of the organs.  Her omentum was removed along with a full hysterecomy, appendectomy, and the removal of some lympnodes.

 

She had labs redrawn December 18, 2012 and her CA125 has risen to 5,427.

 

Please help me to understand this.  In my mind, I was expecting to see the number somewhat lower.

 

Thank you,

Sheila