Reported in the Journal Of Angewandte Chemi---from China's Cancer Research Program, they are using Iridium, one of the most dense elements. I cannot get into the paper. You have to be a Member of a Medical Organization, and I think a Translation was done in Europe. I got a blurred paper in Chinese.
But the way they use it, as I understand it, is they are reacting Iridium, with an un-named organic molecule. This is injected into the blood--where O-, instead of the normal O2 Oxygen molecule is released. From a chemistry point of view, I can see that if they have an Oxygen stripped of one of its negative 2 valances--this would create a violent oxidant, looking for a home. So according to what I can gleam, this O- enters cancer cells, but not normal cells, and the cancer cells just die instantaneously.
Maybe our Colleague Patrick, can get the paper., through his research computer skills.
Over there, they considered this to be a major breakthrough. Iridium is hard to get as it is one of the rarest of the Earth Metals.