Rising CEA tumor marker

@conyankee - I’m sorry for the worry about your wife’s rising CEA despite positive scans, conyankee. I’m not a doctor, but I can offer insights to guide discussions with her oncologist. Your wife’s lung tumor shrank from 6 cm to 3 cm on Tagrisso (40 mg, 9 months) with radiation, and PET/MRI shows no cancer in lymph nodes, adrenal glands, or brain. Yet, her CEA is over 500, which is concerning.
Rising CEA with negative scans may have several causes. Inflammation from radiation (pneumonitis, affecting 10–30% of patients) or liver issues (Tagrisso-related toxicity in 25%) can elevate CEA without cancer progression. Lab errors or conditions like COPD are also possible. Alternatively, early Tagrisso resistance (e.g., EGFR C797S mutation) or micrometastases below PET detection (< 1 cm) could explain it, though resistance is less likely at 9 months with tumor shrinkage. Rarely, a new cancer (e.g., colorectal) could raise CEA.
Encourage your wife to ask her oncologist about repeating the CEA test, checking inflammatory markers (e.g., CRP), or ordering a liquid biopsy to detect resistance mutations (found in 30–50% of progression cases). Additional imaging (e.g., CT) or monitoring CEA trends over 4–8 weeks may clarify. A second opinion from an NSCLC specialist could help.
The scan results are encouraging, but the CEA rise needs urgent evaluation. Discuss potential non-cancer causes and resistance testing. I can help draft questions for the oncologist if needed. Do you feel comfortable at approaching your doctor with these questions?

Thanks so much for your thoughtful analysis. Will discuss all of the possible reasons you mentioned for the CEA rise with her oncologist