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KRAS G12C colorectal cancer (RAS-mutant)
If your tumor has a KRAS or NRAS change, some drugs won't help, but others will. And for the G12C change, there are now targeted pills made for your cancer.
ℹ️ General information to help you and your loved ones talk with your care team, not medical advice. Read our disclaimer.
The quick guide
What it means: The tumor has a mutation in KRAS or NRAS (RAS-mutant). G12C is one specific KRAS change found in about 3 to 4% of colorectal cancers.
How it's found: A gene test on tumor tissue or blood. RAS testing is recommended for all metastatic colorectal cancers.
How common it is: About half of colorectal cancers are RAS-mutant; KRAS G12C is about 3 to 4%.
How treatment works
🌱 Early-stage
- Early-stage RAS-mutant cancer is treated like other early colorectal cancer (surgery, then chemo when needed).
🔁 Advanced or metastatic
- First line: chemo (FOLFOX, CAPOX, FOLFIRI, or FOLFOXIRI), often with Avastin. EGFR antibodies (Erbitux, Vectibix) don't work alone for RAS-mutant tumors.
- Second line and later (KRAS G12C): Krazati (adagrasib) plus Erbitux (cetuximab), or Lumakras (sotorasib) plus Vectibix (panitumumab).
- Later lines: Lonsurf with Avastin, Stivarga or Fruzaqla.
Approvals depend on stage and prior treatment. Your care team will decide what fits you.
Drug guides
- Krazati (adagrasib)
- Lumakras (sotorasib)
- Erbitux (cetuximab)
- Vectibix (panitumumab)
- Avastin (bevacizumab)
- Eloxatin (oxaliplatin)
- Camptosar (irinotecan)
- Lonsurf (trifluridine and tipiracil)
- Stivarga (regorafenib)
- Fruzaqla (fruquintinib)
Biomarker tests that matter
Side effects you may notice
- Diarrhea (loose, watery stools)
- Nausea and vomiting (CINV)
- Fatigue (extreme tiredness)
- Dermatitis (skin rash and skin changes)
- Neuropathy (numbness and tingling)
❓ Questions you and your loved ones can ask
- Is my KRAS change G12C?
- When would Krazati or Lumakras be an option?
- What skin care should I start with the EGFR antibody?
Back to Colorectal cancer overview. Other types: Colon cancer: non-metastatic and metastatic, Rectal cancer: early, locally advanced and metastatic, MSI-high / dMMR colorectal cancer, HER2-positive (HER2-amplified) colorectal cancer, RAS wild-type colorectal cancer (KRAS/NRAS normal), BRAF V600E colorectal cancer.
Written by the Cancer Side Effects Guide team from FDA labels and leading cancer centers. Not medical advice. · Last updated: October 15, 2026 · How we write
Sources
Last updated: October 15, 2026. We summarize these sources in our own words.