A study to learn how well tucatinib plus trastuzumab works for treating participants with metastatic colorectal cancer, and how safe it is: a plain language summary of the MOUNTAINEER study.

Abstract

This is a summary of an article describing an ongoing study called MOUNTAINEER. This article was published in The Lancet Oncology in 2023. The study included 117 adults with metastatic HER2-positive colorectal cancer. The researchers wanted to know whether a combination of 2 drugs called tucatinib and trastuzumab could shrink the participants' cancer. The researchers also wanted to know whether receiving tucatinib alone could also shrink the participants' cancer. In this study, researchers found that 32 out of 84 participants had their tumors respond to treatment with tucatinib with trastuzumab. This was about 4 in 10 participants. This means that the tumors shrank by at least 30% or disappeared. Participants whose tumors responded to tucatinib with trastuzumab responded for a median of 12.4months. 60 out of 84 participants had their tumors respond or remain about the same size after treatment with tucatinib with trastuzumab. This was about 7 in 10 participants. For those who received tucatinib with trastuzumab the median length of time participants lived during the study was 24.1months and the median length of time participants lived during the study without their cancer growing or spreading was 8.2months. 1 out of 30 participants had their tumors respond to treatment with tucatinib alone within 12weeks. 19 out of 86 participants who received tucatinib with trastuzumab had serious medical problems, also called serious adverse events. This was about 2 in 10 participants. Not all of these serious adverse events were related to tucatinib with trastuzumab. 3 out of 30 participants who received tucatinib alone who had serious adverse events. This was 1 in 10 participants. Not all of these serious adverse events were related to tucatinib alone. Tucatinib with trastuzumab could be a good treatment option for people with HER2-positive colorectal cancer that has spread to other parts of the body. On January 19, the Food and Drug Administration (FDA) granted accelerated approval to the combination of two targeted drugs, tucatinib (Tukysa) and trastuzumab (Herceptin) for people with HER2-positive colorectal cancer that is metastatic or that cannot be treated with surgery. The FDA can grant accelerated approval for new treatments that fill unmet needs for patients with serious medical conditions. Clinical Trial Registration: NCT03043313 (MOUNTAINEER study) (ClinicalTrials.gov).