KRAS Mutations Match in Almost All Tumors

If there is a KRAS mutation in the primary colon or rectal tumor, there is almost always a matching mutation when that tumor spreads to the liver.

Researchers in the Netherlands tested both tumors for KRAS mutations in over 300 patients whose cancer had spread to their livers.

They found about a third of patients had KRAS mutations and KRAS status matched in 96 percent of the cases, making it possible to test either tumor to make decisions about treatment with Erbitux® (cetuximab) or Vectibix® (panitumumab)

Out of 305 tumors:

  • 108 had a KRAS mutation in either the primary colorectal or metastatic liver tumor (35.4 percent)
  • KRAS mutations didn’t match in 11 of the 108 (3.6 percent)
  • Of those:
    • 5 had a wild-type (normal) primary and KRAS mutation in the liver metastasis
    • 1 had a KRAS mutated primary and the liver met was wild-type
    • 5 had different KRAS mutations in the primary and liver tumors.

Nikki Knijn and her team at the Nijmegen Medical Centre in the Netherlands concluded,

We observed a high concordance of KRAS mutation status of 96.4% (95% CI 93.6–98.2%) between primary colorectal tumours and their corresponding liver metastases. In only six patients (2.0%; 95% CI 0.7–4.2%), the discordance was clinically relevant. In this largest and most homogenous study to date, we conclude that both primary tumours and liver metastases can be used for KRAS mutation analysis.

SOURCE:  Knijn et al., British Journal of Cancer, Published online March 1, 2011.

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