Targeted Therapy for Colorectal Cancer: — What Your RAS, BRAF and HER2 Results Mean

A tumour that is RAS mutated, BRAF wild-type, HER2 negative and MSI-low still has treatment options. Anti-angiogenic agents — which target the blood supply the tumour needs to grow — can be added to a chemotherapy backbone regardless of these biomarker results, and NCCN guidance supports their use in this setting. Being negative on the targeted-therapy panel is common in colorectal cancer. It narrows the menu but does not close it, and your oncologist will discuss what a chemotherapy-based regimen combined with anti-angiogenic treatment is expected to achieve in your case.

The mutations found in your primary tumour may not match exactly what is in a metastatic site or in the tumour after treatment. If your cancer progresses on a regimen, your oncologist may recommend a repeat biopsy of the new or growing lesion. Re-testing is particularly relevant for HER2, where status can differ between sites, and for anyone whose earlier sample was too small for complete analysis. NCCN and ESMO both recognise that molecular profiles can shift, and that re-testing at progression is a reasonable step when it would change the treatment decision.

They work by different mechanisms. Chemotherapy attacks all rapidly dividing cells, which is why it affects hair follicles and the gut lining alongside cancer cells. Targeted therapy is designed to interfere with a specific molecule or pathway the tumour depends on — which is why the mutation result matters before it is used. The side effects are also different: each drug class has its own toxicity profile, and your oncologist will explain what to watch for before you start. Many colorectal cancer regimens combine both, so you may receive targeted therapy and chemotherapy at the same time.

Wild-type means no mutation was found in the RAS genes tested. For patients with RAS wild-type colorectal cancer, NCCN and ESMO guidance supports the use of anti-EGFR antibodies as part of the treatment regimen — drugs that block a growth signal the tumour relies on. This makes RAS wild-type a meaningful positive finding, not just an absence of a mutation. Your oncologist will also consider where in the bowel the primary cancer arose, because left-sided and right-sided colorectal cancers can respond differently to anti-EGFR therapy even within the wild-type group.

Ask for a copy of the molecular pathology or biomarker report in writing. This is your right as a patient, and your oncology team should explain each result and what it means for your treatment. The report typically lists each marker tested, the result, and often an interpretation. If anything is unclear, ask specifically: what was tested, what the result was, and what that result opens or closes. A second opinion on the molecular interpretation — not just the diagnosis — is always reasonable, and a copy of the report makes that straightforward to arrange.

Yes. Targeted therapy infusions for colorectal cancer are given as day care at CION centres. Your oncologist will arrange the required biomarker testing on your tumour tissue through a pathology laboratory before deciding which regimen is appropriate. Response-assessment imaging, including PET-CT where indicated, is coordinated with partner imaging centres. CION does not provide CAR-T or cell therapy; if that becomes relevant to your case, a referral to a specialist centre would be discussed with you.