CA 27.29 rising. Is chemotherapy effective? Should regime be changed?

I am 47 years old. I had a lumpectomy and lymph node dissection.  Five lymph nodes were positive.  My cancer is Her2nue strongly positive and estrogen and progesterone negative.  I started combination chemotherapy with Doxil, Cytoxan, and Taxotere every 3 weeks.  I have recently completed treatment 5 of 8.  

The Doxil was reduced due to PPE. Doses were 50,45,45,35,35. The PPE continues, but less severe.

My bloodwork for breast cancer antigen CA27.29 concerns me.  The test has been repeated before each treatment and the results are: 9-17-33-26-28.  Should I be concerned?  Should changing my treatment be considered?

Our plan was to complete this course, then follow with radiation, and then additional chemo possibly including Herceptin.

[CCF-RN,MSN-JS]

Dear Her2nue:  The validity of the CA27.29 is still very controversial.  In many clinical settings, this test is not done because it is too difficult to interpret results.  In the absence of other information that would confirm disease progression, it makes sense to stick with the current plan.  The CA27.29 may not be a reliable enough test on which to base independent clinical decisions.