What Causes Elevated CEA Levels After Taking Chemotherapy?

I have a question regarding tumor markers. I just finished chemo TCH(doctaxel, carboplatin and herceptin) stage 2a, node negative, bilat-mastectomy.no lymphovascular invasion and main tumor surrounded by DCIS EIC (at least 25% of all tumor was not invasive by definition) All scans PET negative 7 months ago, brain MRI negative, liver Ultrasound also negative. Did have medication drug induced hepatitis due to levaquin for 45 days in December (chemo caused expander infection and had to be removed) with elevated enzymes (all 3 alp, ast, alt) but have improved within normal range each week during past 6 wks. My CEA was 1.5, ca 15-3 was 5.1 3 months ago, yesterday, day before last chemo basically the same; CEA 1.6 and Ca 15-3 at 6.2. and, todat 3 weeks after last chemo CEA 1.0 and CA 15-3 7.5 (just under one point in 3 weeks and 2.4 points in 4 months. Normal ranges are 2.5 for CEA and 32 for CA 15-3. They are pretty low which is good and my onc said it was ok and not to worry because epithelial tissue also sheds ca 153- so is never zero.My question is if you agree that this little elevation is just a normal variation because is not even 1/4 of Upper normal limit.And if the medication induced hepatitis can be a factor on this mild raise because hepatitis can also raise ca 15-3? I'm just worried