Well, I have bittersweet feelings. My sister CEA dropped to 6.1 from 6.9 (two weeks ago, <5 is normal range). Her PET didn't light up, which is good. However the TAC images of the test showed some small lung nodules (both lungs), compatible with recurrence (according to the radiologist). The radiologist also said that they may be too small to light up in the PET (the bigger one is 5mm). So, her oncologist is not too worry since her CEA dropped again and is planning on getting her CEA every two weeks to see the trajectory. He also wants to get her a CT scan in 6 weeks. My sister was happy with the plan, and that is the most important.
I had a theory about the fluctuating values of CEA of my sister. When my brother-in-law and my other sister ( they smoke) are visiting Maria, her CEA increases. When they leave, CEA drops. They live in a different city, and this summer went to visit Maria two times (the two times CEA increased). I am not sure about my theory now, since new lung nodules have appear in the equation