Eric's post is an interesting one which describes an other attempt to use viruses or in this case bacterias to target directly cancer cells or to ellicit an indirect immune system response.
To some degree it is a modern scientific approach similar to a much older empiric treatment developped by Dr Coley called
Coley's mixed bacterial vaccine.
It made use of 2 dead bacterias which caused flu like symptoms for a few days with high temperature fever. Some treatment successes were reported & according to my recollections of a book which gathered the medical data of Dr Coley's patients the average of favorable outcomes was similar to or better than that of conventional treatments of that time.
The apparent efficacy (not proven in clinical trials) of Coley's regimen was attributed to an immune response to the bacterias which caused cancer cell suppression & to the effect of the fever since it is known that cancer cells are sensitive to temperatures approching 42 degree Celcius.
http://en.wikipedia.org/wiki/Coley's_Toxins