What is dexamethasone for and how do ctDNA and PET scan results compare?

Dexamethasone is a steroid medication that helps reduce inflammation and can be very effective for preventing nausea and vomiting during cancer treatment. Having a PET scan show no cancer detected is encouraging news, and ctDNA tests can sometimes detect microscopic amounts of cancer DNA in the blood that imaging might not pick up - both tests provide valuable but different types of information that the medical team uses together to guide treatment decisions.

Don I'm so sorry you are going through this. I have state 4 CRC and have had many anti-nausea drugs, including dexamethasone. They usually give the dexamethasone before an infusion as a boost to help with nausea. Be sure your husband doesn’t take the oral anti-nausea before the time the nurses say or he could get too much. Also, I’ve had ctDNA & PET scans. The ctDNA maps the DNA of original tumor, then looks for that DNA in the bloodstream at specific intervals (1 month or 3 months usually). If the ctDNA number goes up, that usually means the original tumor is growing. The ctDNA test usually picks up activity before any scans. But insurance usually doesn’t cover it (I think medicare may). The ctDNA test picked up a tumor in my liver before a CT did. Once they knew to look, they did more detailed imaging (MRI & PET scan) and found it. It won’t tell them WHERE to look though ~ just that it’s likely growing SOMEWHERE. Good luck and let us know how your husband is doing.

My husband passed away on June 21,2026

Don I am so sorry to hear this. I knew this was an older post and had not seen your posts in the other forums with this information. I’m likely facing passing myself and leaving my husband and son alone. I cannot image the loss you’re feeling right now. Take care of yourself ❤️