significance of elevated liver function

[Alexis in Virginia]

I just received my 3rd A/C treatment on a dose dense schedule yesterday.  I am 38 yrs old and had a mastectomy for extensive DCIS and 1.6 cm invasive cancer with auxillary lymph node dissection (1 positive node) - all clean margins.  I had immed. free TRAM reconstruction with very nice results and no complications other than a 15 hr surgery with some blood loss so I had 2 blood transfusions over the first 2 days post-op in ICU + 3 more days in hosp.   I started chemo about 5 weeks post-op.  My treatment plan is every other week- 4 doses A/C followed by 4 doses Taxol.  I have had very mild side effects and have responded very well to the Neupogen to raise my WBC (4 doses raised my NEU from 342 to 30,700).  
My concern now is my liver function. Here are my levels:
          8/25      9/22     10/5     normals
AST       23        90      ~70         35
ALT       31       247      ~150        40
Alk Phos  88       165        ?         125

Yesterday my oncologist gave me the option of delaying treatment #3 or substituting an encapsolated sister drug for the Adriamycin.  We are trying the other drug and will retest liver function next week.
My questions are what are the safe limits on liver function or is duration of elevated levels more significant?  I was told that we may have to rethink if I will be able to handle the Taxol as well.  I am concerned the substituted drugs may not be as effective etc.  Why, when I have had no liver problems and I don't drink or take any other meds, is my liver having such a hard time with the chemo? Might this indicate other problems?

[CCF-RN,MSN-rf]

Dear Alexis in Virginia:  Liver enzymes can become elevated for a variety of reasons, including some chemotherapy.  It is important for your doctor to evaluate this within the context of your specific situation.