American Board of Internal Medicine (ABIM) Certification Practice Exam

What is the primary component of most chemotherapy regimens used in colorectal cancer?

1. Oxaliplatin

2. Cyclophosphamide

3. 5-FU

4. Docetaxel

The correct answer is: 5-FU

5-fluorouracil (5-FU) is the primary component of most chemotherapy regimens used in the treatment of colorectal cancer. This antimetabolite drug works by inhibiting thymidylate synthase, which is crucial for DNA synthesis and repair. By interfering with these processes, 5-FU effectively prevents cancer cells from dividing and growing. 5-FU can be used alone or in combination with other agents, such as leucovorin and oxaliplatin, to enhance its effectiveness. The combination regimens that include 5-FU, such as FOLFOX (5-FU, leucovorin, and oxaliplatin) and FOLFIRI (5-FU, leucovorin, and irinotecan), are well-established in clinical practice for treating colorectal cancer and have shown improved outcomes in patient survival. Cyclophosphamide is primarily used in hematological malignancies and not a frontline treatment for colorectal cancer. Oxaliplatin is indeed used in combination regimens but is not the foundational agent. Docetaxel is primarily used for solid tumors like breast and lung cancers, making it less relevant for colorectal cancer treatment. This context solidifies the role of 5-FU as the cornerstone