In one embodiment, the invention provides a method of treating a subject who suffers from a neoplasm (including a cancer such as a radiotherapeutic-resistant cancer) by administering to the subject a therapeutically effective amount of (a) 5-formyl-2′-deoxyuridine (fdU or foUdR) or a 5-formyl-2′-deoxyuridine derivative, optionally in combination with 5-hydroxy-2′-deoxyuridine (hUdR); and (b) at least one composition selected from the group consisting of either 5-fluorouracil (5-FU), a 5-FU prodrug (e.g. 5-fluoro-2′-deoxyuridine (FdU)) or 5-FU metabolite. In a preferred embodiment, a subject who suffers from colorectal cancer (CRC) or metastatic colorectal cancer (mCRC) is treated with a therapeutically-effective amount of fdU and either 5-FU or the 5-FU prodrug 5-fluoro-2′-deoxyuridine (FdU). Related pharmaceutical compositions are also provided.