Mutations and biomarkers

KRAS mutation: what it means for your treatment

What does it mean that my tumour has a KRAS mutation?

2 min read Updated: 01/11/2026 Reviewed by: Equipo CRC Warriors Last reviewed: 01/11/2026
Prepare my appointment

In short

Almost half of colorectal cancers carry a mutation in the KRAS gene. Today the most important consequence is that anti-EGFR antibodies (cetuximab, panitumumab) do not work, so they are not used. Chemotherapy and anti-angiogenic drugs work just as well, and for the G12C variant targeted drugs already exist.

In this guide
  1. What KRAS is
  2. Why it is tested
  3. Which treatments do work with mutated KRAS
  4. Drugs that target KRAS
  5. What to ask at your appointment

What KRAS is

KRAS is a gene that makes a protein working as a growth switch inside the cell. When it is mutated, the switch is stuck "on" and the cell divides without control. Between 40 % and 45 % of colorectal cancers have a KRAS mutation; the most frequent are G12D, G12V and G13D. The G12C variant is less common in colon cancer (3-4 %) but is the one with the most new drugs.

The mutation is only in the tumour; it is not hereditary and is not passed on to children.

Why it is tested

Guidelines recommend testing RAS (KRAS and NRAS) and BRAF in all patients with metastatic disease, and MSI status in all stages, because it changes treatment:

  • If KRAS (or NRAS) is mutated, anti-EGFR antibodies (cetuximab and panitumumab) are not effective and may even be harmful. That is why they are not part of your treatment.
  • If KRAS and NRAS are normal ("RAS wild-type"), those antibodies are an option, especially in left-sided tumours.

Which treatments do work with mutated KRAS

  • Chemotherapy (FOLFOX, FOLFIRI, CAPOX, FOLFOXIRI) works the same as in tumours without the mutation.
  • Anti-angiogenic drugs (bevacizumab and, in later lines, aflibercept, ramucirumab) are combined with chemotherapy.
  • In later lines: trifluridine/tipiracil (with or without bevacizumab), regorafenib and fruquintinib.
  • If the tumour is also MSI-H/dMMR, immunotherapy is the first option, regardless of KRAS.

Drugs that target KRAS

For decades KRAS was considered "undruggable". That has changed:

  • KRAS G12C: sotorasib and adagrasib block the mutated protein. In colorectal cancer they work much better combined with an anti-EGFR (panitumumab or cetuximab); this is how they were approved in the United States and they are being adopted in Europe. Ask about availability at your hospital or about trials.
  • KRAS G12D and pan-RAS: several drugs are in phase 1-3 trials (for example G12D inhibitors and so-called pan-RAS inhibitors). They are not yet approved, but if your tumour has these variants it is worth checking the trials open in Spain.

What to ask at your appointment

  • Which exact KRAS variant do I have (G12C, G12D, G12V, G13D…)?
  • Have NRAS, BRAF, HER2 and MSI status also been tested?
  • Is there a clinical trial for my variant that I could join?
  • If I progress on the current chemotherapy, what is the planned next step?

Frequently asked questions

Does mutated KRAS mean a worse prognosis?

Overall, KRAS-mutated tumours have a somewhat worse prognosis than RAS wild-type ones, partly because fewer targeted therapies are available, but the difference is moderate and depends a lot on the variant and other factors. BRAF V600E, not KRAS, is the mutation with the greatest prognostic impact.

Can KRAS status change over time?

The tumour's original mutation does not disappear. What does happen is that, after anti-EGFR treatment, some RAS wild-type tumours acquire RAS resistance mutations; that is why the test is sometimes repeated on a liquid biopsy before using those drugs again.

Where does my report say whether I have mutated KRAS?

In the pathology or molecular biology report, in a section usually called "RAS study" or "NGS panel". It appears as "KRAS mutated (p.G12D)" or "KRAS wild-type". If you cannot find it, ask for it: you are entitled to a copy.

Next step

What can you do now?

Are there clinical trials for your case?Enter your stage, mutations and province and we tell you which trials you meet and why. No account needed, two minutes.Find trials for my profile Take your questions to the appointmentWrite down your questions on this topic in a sheet ready to print or show on your phone.Prepare my appointment

We will let you know when there is news

No account needed: just your email. One weekly email, only when there is something new. Unsubscribe in one click.

We will only use your email for these alerts. CRC Warriors Association, non-profit. Privacy

Sources · 4 sources consulted
  1. ESMO Clinical Practice Guideline — Metastatic colorectal cancer (2023)
  2. SEOM — Cáncer de colon y recto
  3. NCI — Cáncer colorrectal: tratamiento (PDQ)
  4. Fakih MG et al. Sotorasib plus Panitumumab in Refractory Colorectal Cancer with Mutated KRAS G12C (CodeBreaK 300). N Engl J Med 2023

Reviewed by: Equipo CRC Warriors · Last reviewed: 01/11/2026.
This guide is general information prepared by the CRC Warriors Association (non-profit) from public sources. It does not replace the assessment of your medical team or professional advice on your specific case. If you spot an error, write to contacto@crcwarriors.org.

More guides on mutations and biomarkers

Keep reading

What does the BRAF V600E mutation mean in colon cancer?

BRAF V600E is found in 8-10 % of colorectal cancers and is linked to more aggressive tumours. The good news is that since 2020 there is a specific ta…

Read guide →

What does it mean that my colon cancer is HER2-positive?

Between 3 % and 5 % of colorectal cancers have too many copies of the HER2 gene, mostly RAS wild-type tumours. It is uncommon, but it matters: there …

Read guide →

What does it mean that my tumour is MSI-H or dMMR?

MSI-H (high microsatellite instability) and dMMR (deficient mismatch repair) describe the same thing: a tumour that accumulates many mutations becaus…

Read guide →

What is an NGS panel and how do I get one done?

An NGS panel analyses dozens or hundreds of tumour genes at once to find alterations that have a treatment. In metastatic colorectal cancer guideline…

Read guide →

What does RAS wild-type mean and why am I being offered cetuximab or panitumumab?

"RAS wild-type" means your tumour has no mutations in KRAS or NRAS. In that case anti-EGFR antibodies (cetuximab, panitumumab) do work, and they work…

Read guide →

What is Lynch syndrome and what should I do if I am diagnosed with it?

Lynch syndrome is the most common hereditary cause of colon cancer: an alteration in one of the DNA repair genes that is passed from parents to child…

Read guide →

This guide is free thanks to members and donors

We write it and keep it up to date as a non-profit patient association. If it helped you, help us write the next one.

Become a memberMake a donation