molecular biologist matthias gromeier, the creator of the virus, is pressing ahead. against a number of other cancers just in a laboratory dish. >> gromeier: yes. >> pelley: what have you been able to kill so far? >> gromeier: so, we have done this for lung cancers, breast cancers, colorectal cancers, prostate cancers, pancreatic cancers, liver cancers, renal cancers. we probably see this in just about any type of cancer you can imagine. >> pelley: the man who's overseeing the polio trial for the f.d.a. is dr. peter marks, a deputy director responsible for hundreds of other experimental treatments for cancer. you have to wonder if it's too good to be true. some of the results in these early trials appear nearly miraculous. >> peter marks: we hope they really are miraculous. we do have to be cautious because, sometimes, people just get lucky, and the first patients they treat with a therapy respond very well. but subsequently, additional patients don't. >> pelley: help me put immunotherapy in perspective here. how big an advance is this in terms of viruses to treat can

>> matthias gromeier: well, i got a range of responses from...ou're lying" to all kinds of things. most people just thought it was too dangerous. >> friedman: oh, i thought he was nuts. i mean, i really thought he was using a weapon that produces paralysis. >> pelley: other researchers are experimenting with cancer treatments using viruses including h.i.v., small pox and measles. but polio was dr. gromeier's choice because, as luck would have it, it seeks out and attaches to a receptor that is found on the surface of the cells that make up nearly every kind of solid tumor. it's almost as if polio had evolved for the purpose. gromeier re-engineered the polio virus by removing a key genetic sequence. the virus can't survive this way, so he repaired the damage with a harmless bit of cold virus. this new modified virus can't cause paralysis or death because it can't reproduce in normal cells. but in cancer cells, it does and in the process of replicating, it releases toxins that poison the cell. duke went to the f.d.a. for approval of this new franke