This paper's results had G12V as the marker of the most successfully treated line (SW480) )of the mutant CRC cell lines tested (vs LoVo for KRAS G13D and HT29 for BRAF V600E), for mutant CRC cells treated with vitamin C.
IV vitamin C temporarily reaches much higher levels in the arteries and veins but (dehyro)ascorbate levels will be lower perfused and transported further in.
Our viable cell lab's sensitivity tests showed that multiple adjuncts (5FU chemo + 2 natural) were necessary to kill less sensitive cancer cells. It seemed surprising then that the resistant CRC cells were not very -iri or -oxi sensitive even without prior treatment. Tissue labs struggled with mutant cell identification, which I suspect has to do with all that cimetidine and IV vitamin C distorting results with those cells that didn't disintegrate and also yielded less CA19-9. However higher bloodlevels of CA199 are often associated with KRAS/BRAF mutations, where serum CA199 is easier to monitor frequently anyway.
In any case, parallel to your situation before surgery, we used oral chemo (5FU base), IV vitamin C, cimetidine and heavy duty supplements in the run up to surgery. Although we used higher vitamin dosages, this list looks useful (
http://catalyticlongevity.org/prepub_archive/Adjuvants-ColorectalCA.pdf, a different list than my usual LEF links). Multiple chemo and supplement ajuncts substantially drove down the most common Kras indicator, CA199, before surgery. In 1-2 months, a working dosage eliminated 85%-95% of the CA19-9 blood level associated with the conglomerated mass that was finally removed. Since then, we also found celebrex very useful to improve oral immunochemo results.