Potentiation of antimetabolite action by alkylating agents.

5-FU is an active antimetabolite widely used in the therapy of human solid tumors. Its antitumor action can be potentiated by alkylating agents and other cytostatic drugs as well. This potentiation is evident in the case of gastric cancer, less manifest in the case of pancreatic cancer, and missing in colorectal cancer. Although 5-FU is a very active drug against breast cancer, its antitumor effect was never really investigated in a rational way with regards to potentiation by other agents. A reevaluation of drug combinations with 5-FU seems to be mandatory in the future.