Impressive progress is being made with gene therapies in the laboratory, as demonstrated by this item from EurekAlert: "researchers have used gene therapy to either completely abolish or significantly inhibit tumor progression in a mouse model of ovarian cancer ... They treated some of the mice immediately with a genetically engineered vaccinia virus containing a gene coding cytosine deaminase, a suicide gene, and delayed treatment of other mice for 30 or 60 days. ... The researchers found complete inhibition of tumor growth in the mice that were treated immediately with gene therapy and significant tumor inhibition in the 30- and 60-day delayed treatment mice." Scientists can now target abnormal cells with great specificity based on their biochemistry, but the real economic barrier for this sort of treatment is the enormous variety in that biochemistry for cancer cells.