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Colorectal CancerApril 2019Summary reviewed May 2026

What the MyPathway Study Found — Trastuzumab + Pertuzumab for HER2+ Colon Cancer

MyPathway tested two HER2-targeting antibodies — pertuzumab and trastuzumab — in 57 people with HER2-amplified metastatic colorectal cancer that had failed standard chemotherapy. About a third saw their tumors shrink.

What the trial was testing

The MyPathway enrolled 57 patients with colorectal cancer. The study was sponsored by Genentech and tracked outcomes across the full group of patients who matched the trial's eligibility profile.

It was initial testing (phase 2). Trials at this stage are designed to produce evidence regulators and physicians can act on — not just observations to follow up later.

What the results showed

32% tumor response rate in heavily pretreated HER2-positive colon cancer.

The Lancet Oncology · 2019 · NCT02091141

These findings — that in heavily pretreated HER2-amplified metastatic colorectal cancer — were published in the The Lancet Oncology and represent the headline result of the study.

Researchers tracked outcomes across 57 patients enrolled in the trial. The result was consistent enough across the group that the team felt confident reporting it.

What this means for patients

For patients with colorectal cancer, this result changes the calculus on what to ask their care team about. Whether it changes day-to-day care depends on factors like disease subtype, prior treatments, and where the patient is in their care journey.

What you can do now

Both pertuzumab and trastuzumab are FDA-approved for breast cancer and available now. The combination is used off-label for HER2-positive colorectal cancer; tucatinib + trastuzumab is now FDA-approved for this specific indication. Ask an oncologist about HER2 testing on your tumor and whether either combination fits.

Eligibility for the treatments mentioned above depends on specific test results and clinical history. Bring this summary, the trial name, and your most recent labs or pathology report to your next visit.