Pembrolizumab in the Treatment of Patients with Microsatellite Unstable Colorectal Cancer

Abstract

Colorectal cancer is one of the most common tumours in the world, with microsatellite instability having an important role in the development of these tumours. Microsatellite instability is responsible for the worse response of tumours to chemotherapy, while also having a role in the better prognosis associated with these tumours. This relates to the higher immune infiltration that results from the high neoantigen load of microsatellite unstable tumours. This highly responsive immune microenvironment seen in microsatellite unstable colorectal cancer makes these tumours great candidates for therapies targeting the immune system, such as immune checkpoint inhibitors. The PD-1/PD-L1 axis is upregulated in colorectal cancer with microsatellite instability, making the blockade of this axis a good therapy alternative for these patients.Pembrolizumab has shown to be an effective PD-1 blocker, with trials showing good responses to this therapy, as seen in the most recent KEYNOTE-177 trial. Conclusion:Colorectal cancer with microsatellite instability is a subtype of tumour with characteristics making it a great candidate for the treatment with immunotherapy, namely with the PD-1 blocker pembrolizumab, enhancing the importance of including this treatment in the options available for these patients.