CEA of 6 is still really low. Did you have colon resection? You said you had metastasis to liver and lymph nodes.... When was your last CT done, what is the current status., what kind of surveillance program are you on?
LONSURF® (trifluridine and tipiracil) is a combination medication used to treat certain cancers. Here are some key points about it:

Indications:
LONSURF is prescribed for adults with colorectal cancer that has spread to other parts of the body (metastatic) and who have been previously treated with specific chemotherapy medicines.
It is also used to treat adults with a type of stomach cancer called gastric cancer, including adenocarcinoma of the gastroesophageal junction, that has spread and was previously treated with at least two types of treatment.

I just talked to my oncologist last week about my situation (the same as yours), and specifically asked about lonsurf. He stated this is no longer considered standard treatment, as it has not been shown to be effective.