Liver Function

My wife is 40 and has metastatic breast cancer. She has numerous
metasases in her liver, and has just completed 12 weeks of chemotherapy (taxol+Herceptin). During the course of the treatment,we were greatly encouraged by her improving liver function tests...(ALT,AST ALKPH are now all in the normal range). She had a CAT scan last week and we went in today expecting good news regarding the metastases, but were told there was only 'slight' improvement in the cancer.

The doctor was puzzled and wanted to check the scan himself (they were done in two different hospitals), and went on to speculate on the reasons for the descrepancy...but led us to believe that he was somewhat surprised.

My question in general is: what is the general consensus on the validity of liver function tests to gauge progress of treatment, and how is it possible to have 'normal' liver function tests but still have substantial liver involvement.

thank you

[CCF-RN,MSN-JS]

Dear Edward: In general increases in ALT, AST and alkaline phosphatase values reflect damage to organs where these enzymes or substances are found in the body.  Tissue damage can be caused by various things not only cancer, for example, certain medications can cause temporary elevations.  These tests are not specific enough to be used as the sole gauge of the progress of treatment.  It is not unusual for there to be substantial liver involvement by tumor yet the liver function tests still can be normal.  

In terms of the ct scans, there can be quite a bit of difference between ct scans done from one institution to another.  A slight improvement in the scans is good news, meaning that the cancer is being controlled at this point.