Trifluridine/tipiracil is a medication used in this clinical trial as an alternative chemotherapy option. It is being tested for its safety and effectiveness in patients with metastatic colorectal or gastroesophageal cancer who have a deficiency in an enzyme called dihydropyrimidine dehydrogenase (DPD). This medication is considered as a replacement for other chemotherapy drugs like 5-fluorouracil and capecitabine, which are typically used in treating these types of cancers. The trial aims to see if Trifluridine/tipiracil can be a safer and effective option for these patients.

Metastatic Colorectal Adenocarcinoma – This is a type of cancer that begins in the colon or rectum and has spread to other parts of the body. It typically progresses through stages, starting from the inner lining of the colon or rectum and potentially moving to nearby lymph nodes and distant organs. The disease can cause symptoms such as changes in bowel habits, blood in the stool, and abdominal discomfort. As it advances, it may lead to more severe symptoms depending on the organs affected by metastasis.

Metastatic Gastroesophageal Adenocarcinoma – This cancer originates in the lower esophagus, gastroesophageal junction, or stomach and spreads to other areas of the body. It often begins in the glandular cells lining these regions and can invade nearby tissues and lymph nodes. The progression of the disease can result in symptoms like difficulty swallowing, weight loss, and chest pain. As it metastasizes, it may affect other organs, leading to additional complications and symptoms.