Forbes -- Drugs toxic enough to kill cancer cells are toxic enough to kill healthy ones, too. How can the poison be targeted? One possibility that has long fascinated scientists is to administer a drug that becomes activated only when exposed to radiation. One treatment for the rare skin cancer cutaneous T-cell lymphoma, for example, involves an interaction between a chemical (psoralen) and ultraviolet light. But the trick is not easily applied to internal cancers, and in any event most therapies involving light-activated drugs have been commercial failures.
