If it regularly infects humans why are there not more spontaneous remissions of at least a small kind. The quest it seems would be to grow it independently and fuse it ongoingly into the body at a rate that the body cannot overcome it until the cancer is gone and according to the article that should not take too much time.
How regular is regular, they don’t say. It might be passed around through every hundredth person or something like that. Also what does it take, intimate contact or the kind of casual contagion that spreads colds? Getting the virus earlier and having it overcome and learned by the immune system might also interfere with it being available when it would do good to a cancer patient.