RESUMEN
Colorectal carcinoma (CRC) is one of the most frequently diagnosed malignancies worldwide with a high mortality rate. CRC is often plagued with significant treatment-related morbidity and mortality, and metastatic progression is common. With the advent of immunotherapy, inoperable and advanced cancers have shown favorable response. Immunotherapy has paved the way for survival of all those with advanced metastatic disease whose treatment was limited to palliative care. We explore the case of a 28-year-old female with advanced metastatic CRC refractory to chemotherapy and targeted therapy, managed with PD-1 inhibitor with complete clinical and pathological response in a relatively short period of time. The notion of upfront immunotherapy for advanced metastatic CRC with microsatellite instability is definitely reinforced by the favorable response seen in our case, and we hope that these findings would help reduce the dependence on chemotherapy as the mainstay therapeutic for advanced CRC.