What the trial was testing
The MOUNTAINEER enrolled 117 patients with colorectal cancer. The study was sponsored by Seagen 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
38% tumor response rate in chemo-refractory HER2+ colon cancer.
The Lancet Oncology · 2023 · NCT03043313
These findings — that in chemotherapy-refractory HER2-positive metastatic colorectal cancer — were published in the The Lancet Oncology and represent the headline result of the study.
Researchers tracked outcomes across 117 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
Tucatinib (Tukysa) plus trastuzumab is FDA-approved and available now for chemotherapy-refractory HER2-positive metastatic colorectal cancer — the first targeted regimen specifically approved for this group. Ask an oncologist about HER2 testing on your tumor.
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.
Open colorectal cancer trials
Study of Pembrolizumab Treatment After CYAD-101 With FOLFOX Preconditioning in Metastatic Colorectal Cancer
The purpose of the CYAD-101-002 study is to assess the safety and clinical activity of CYAD-101 in patients with unresectable metastatic colorectal cancer administered concurrently with FOLFOX chemotherapy, followed by pembrolizumab treatment.
Dostarlimab for Locally Advanced or Metastatic Cancer (Non-colorectal/Non-endometrial) With Tumor dMMR/MSI
The goal of this open-label randomized, multicenter, comparative phase II trial is to evaluate the efficacy of the immunotherapy, dostarlimab, as first-line treatment for deficient mismatch repair (dMMR)/microsatellite instability (MSI) non-resectable metastatic or locally advanced non-colorectal and non-endometrial cancers compared to the standard of care chemotherapy. Adult patients (aged ≥18 years) with histologically confirmed dMMR/MSI duodenum and small bowel adenocarcinoma, gastric and oeso-gastric junction (OGJ) adenocarcinoma with combined positive score (CPS)\<5, pancreatic adenocarcinoma, ampulla of vater adenocarcinoma, adrenocortical carcinoma, carcinoma of unknown primary site, neuroendocrine carcinoma (Grade3) all primary, and soft tissue sarcoma (except Gastro-Intestinal Stromal Tumor) will be included in this study. They will be randomized and treated with either dostarlimab (experimental arm A), or chemotherapy (control arm B). Patients with documented disease progression following the first line chemotherapy (Arm B) may be eligible for crossover to be treated with dostarlimab, with the same schedule as arm A.