A system for treating a diseased site in a human or animal body. The system includes a pharmaceutical carrier including one or more phosphors which are capable of emitting light into the diseased site upon interaction, a photoactivatable drug for intercalating into DNA of cells at the diseased site, one or more devices which infuse the diseased sited with the photoactivatable drug and the pharmaceutical carrier, an x-ray or high energy electron source, and a processor programmed to control a dose of x-rays or electrons to the diseased site for production of light inside the tumor to activate the photoactivatable drug.