When did you start taking cimetidine ?
The first CA199 test, best before chemo or radiation or surgery, can be used to improve a guess whether cimetidine should help interfere with your cancer cells' metastasis and immune defeating processes or not. A CRC patient whose cancer tissues are high in both CA199 and CSLEX1 markers is a very high risk patient, likely due to high HIF-1a, or HIF-2a content/activity, and likely having (some or many) KRAS mutant or BRAF mutant cells.
If the CA199 test is less than 2, at any time, the Japanese intepretation was that cimetidine biologically, categorically couldn't help long term 5FU treatment, about 8-10% of CRC patients.
As the unstimulated test values increase, the likelihood of CA199 values reflecting bad cancer processes rises. Thyroid problems, inflammation, excess sugarm chemo, radiation can stimulate CA199 blood values, hence the extra panels. If various extra panels are steady then CA199 readings are likely directly comparable, like CEA. Some less drastic diseases or other cancer may increase CA199. The Japanese results suggest that cimetidine for CA199 helps other cancer somewhat too.
If there is a really serious question about cimetidine utility, then stain the pathology samples for CA199 and CSLEX1. The Japanese research published in the 2000s shows them to be far better companion markers for cimetidine than any tests he has for Erbitux.
Western research is simply studying these selectin (t)issues to death (guess whose...), presumably for new expensive answers. 2017
In competent hands, Matsumoto (2002
) and the subsequent Japanese papers are like a Rosetta stone. If I recall correctly, Life Extension Foundation started sounding the clarion about cimetidine in the 1980s, sialyl Lewis epitopes (selectins) in the late 1990s, and then recommending Imclone (long merged away) for the staining DIY.