TAS-102 is primarily used in the treatment of metastatic colorectal cancer, particularly in patients who have not responded to or have stopped responding to other forms of chemotherapy. It combines two active components that work together to inhibit the growth of cancer cells. One component interferes with DNA synthesis, preventing cancer cells from multiplying, while the other component helps maintain the therapeutic effect by inhibiting the breakdown of the first component. This dual-action mechanism makes it a valuable option for patients with advanced stages of the disease. Additionally, TAS-102 has shown promise in clinical trials for treating other types of cancer, such as gastric cancer, expanding its potential applications in oncology.