Which types of cancer can 5-fluorouracil be used to treat?

5-fluorouracil (5-FU) is an antimetabolite chemotherapy drug primarily used to treat various solid tumors. The correct option accurately identifies the cancers that 5-FU is commonly utilized for, which include colon, rectal, breast, stomach, and pancreatic cancers.

The mechanism of action for 5-FU involves inhibiting the synthesis of thymidine, a nucleotide essential for DNA replication. This action makes it particularly effective against rapidly dividing cancer cells, which is characteristic of the malignancies listed in the correct choice. For example, 5-FU is widely used in the treatment of colorectal cancers, which are among the most common cancers treated with this drug. It is also a standard part of the treatment regimen for breast cancer, particularly in metastatic cases, and is frequently employed in combination therapies for stomach and pancreatic cancers.

The other types of cancers mentioned in the other choices, such as testicular cancer and small cell lung cancer, typically require different treatment protocols, often involving platinum-based agents or other chemotherapy combinations that are more effective for those specific malignancies. Additionally, prostate and ovarian cancers, as well as brain tumors and myeloma, also have distinct treatment approaches that do not primarily include 5-FU.