Among the six cases with liver metastasis, KRAS mutation disappeared in the duration of stable disease or a partial response, and reappeared at the time of progressive disease.
In two patients with K-RAS mutations pretreatment, posttreatment plasmas were evaluated: a patient with clinical progressive disease retained the mutant DNA, while in a patient with a complete response (CR), the K-RAS mutation was no longer detectable.
Three patients with a persistently positive K-ras gene mutation in pre- and post-treatment plasma samples were likely to show early recurrence or have a progressive disease.