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HER2-positive (HER2-amplified) colorectal cancer

HER2-positive colorectal cancer is rare, but finding it matters: it opens the door to targeted treatments that can help you keep doing the things you love.

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 cancer cells make too much HER2 protein (HER2 amplification). It's usually found in RAS wild-type tumors.

How it's found: Testing for HER2 is recommended for metastatic colorectal cancer, using a tissue stain (IHC), ISH, or a gene panel (tissue or blood).

How common it is: About 3 to 5% of metastatic colorectal cancers.

How treatment works

🌱 Early-stage

Early-stage HER2-positive colon or rectal cancer is treated the same as other early colorectal cancer (surgery, and chemo such as FOLFOX or CAPOX when needed).

🔁 Advanced or metastatic

First line: standard chemo (FOLFOX, CAPOX or FOLFIRI), often with a targeted antibody, depending on RAS status and tumor side.
Second line and later: HER2-targeted treatment, such as Tukysa (tucatinib) plus Herceptin (trastuzumab) for RAS wild-type tumors after chemo, or the antibody-drug conjugate Enhertu (trastuzumab deruxtecan).
Later lines: Lonsurf (often with Avastin), Stivarga or Fruzaqla.

Approvals depend on stage and prior treatment. Your care team will decide what fits you.

Drug guides

Biomarker tests that matter

Side effects you may notice

❓ Questions you and your loved ones can ask

Has my tumor been tested for HER2?
Is my tumor RAS wild-type?
When would HER2-targeted treatment make sense for me?

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, KRAS G12C colorectal cancer (RAS-mutant), 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

Not medical advice. This page is general information to help you talk with your care team. It can't replace advice from your doctor or nurse. If you have a fever of 100.4°F (38°C) or higher during treatment, or any symptom that worries you, call your care team now. In an emergency, call 911.