A 64-year-old man undergoes colonoscopy as part of the national CRC screening programme. An exophytic adenocarcinoma is found in the ascending colon.
Staging CT of the chest, abdomen and pelvis is performed, which demonstrates the primary tumour and multiple liver lesions. Following review in the CRC multidisciplinary meeting, the diagnosis is confirmed as CRC with liver metastases that are not amenable to surgical resection. When considering cetuximab in the adjuvant treatment of metastatic CRC, which of the following statements is most accurate?
1- KRAS mutation testing should be performed on samples from both primary and metastatic tumours.
2- Cetuximab should be considered alongside conventional chemotherapy.
3- Cetuximab should be considered if the KRAS gene is wild-type on genetic testing of the primary tumour.
4- Cetuximab should be considered if the KRAS gene is mutated on genetic testing of the primary tumour.
5- Cetuximab should be considered if the KRAS gene is mutated on genetic testing of both primary and metastatic tumours.
Answer 3.
ReplyDeleteCetuximab should be considered if the KRAS gene is wild-type on genetic testing of the primary tumour.
Mutations of KRAS occur relatively early in the adenoma
to carcinoma sequence, and there is good concordance
in the mutation status of primary and metastatic
disease. Genetic testing of KRAS can therefore be performed on the primary tumour only. Cetuximab has been
shown to reduce the risk of progression of metastatic
CRC, but this effect is limited to patients with KRAS wildtype
tumours.
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