The biopsy or resection specimen tissue are stored by the pathology laboratory for at least ten years. The tissues/cells are embedded (moulded) in paraffin wax block. This means that the test can be undertaken on this “archive” material at any stage in the future if disease becomes evident at a different place in the body (metastatic disease).
Testing for RAS gene mutations is very important in determining the best form of...
The biopsy or resection specimen tissue are stored by the pathology laboratory for at least ten years. The tissues/cells are embedded (moulded) in paraffin wax block. This means that the test can be undertaken on this “archive” material at any stage in the future if disease becomes evident at a different place in the body (metastatic disease).
Testing for RAS gene mutations is very important in determining the best form of treatment for metastatic colon and rectum (colorectal) cancer, also called stage four colorectal cancer. RAS is involved in passing signals within tumour cells which result in growth of the tumour. The gene which is responsible for RAS signalling occurs in two different forms; mutated (abnormal) and wild-type (normal).
Approximately 40% of patients with metastatic colon cancer have a tumour with a mutated RAS gene. These patients are unlikely to respond to treatment with anti-epidermal growth factor receptor therapies such as cetuximab and panitumumab. Treatment using these drugs is not recommended for patients with mutated RAS gene as they would suffer from unwanted side effects of the drug without getting any benefit.
Patients with metastatic disease who have normal (wild-type) RAS genes are likely to respond to either cetuximab or panitumumab.
In the UK, RAS gene testing is recommended in all patients with metastatic colorectal cancer. There is a good correlation between RAS gene mutation status in the primary tumour and metastases. Stored biopsies or resection specimens of the primary tumour taken months or years before the onset of metastatic disease can be tested for RAS gene mutation at a later date.
Recently, mutated KRAS genes in advanced non-small cell lung cancer, has been shown to respond to sotorasib (Lumykras) targeted treatment. Sotorasib works by binding to the abnormal KRAS G12C to stop the cancer cell from dividing and growing. About 13% of non-small cell lung cancers have the KRAS G12C mutation.
How is the sample collected for testing?
A sample of cancer tissue is obtained by doing a fine needle aspiration, needle , or surgical biopsy/excision
Is any test preparation needed to ensure the quality of the sample?
No test preparation is needed.
