First of all I'd like to start by saying I am in NO way shape or form saying these horrible experiments could be at all justified.
But given that the Nazi doctors did do intensive experimentation on prisoners in the concentration camps, did any of their testing directly or indirectly lead to breakthroughs in modern medicine?
Yes, although there has been much ethical discussion in regards to using the data from these experiments. Other have discredited the data because they claim that the scientific methods used in the experiments are inconsistent (I'm not saying there were, or weren't). An example of Nazi test results being reviewed in a scientific context is the data collected by Dr. Sigmund Rascher, in the Dachau camp. He experimented with the effects of hypothermia, and how to treat it. While much of the documentation was lost, it was possible to recover enough to evaluate the program, and Leo Alexander investigated the Dachau hypothermia experiments and he wrote a report on it, including a lenghty personal commentary. In recent years it has been suggested that the entirety of the experiments are unscientific and unusable, but they have still served to raise the ethical question of the usage of data obtained in such a manner.
Long story short, it's quite a complex debate, due to the ethical issues, and the scientific premise of the experiments, but I've learned that some researchers have found some utility in Nazi data on hypothermia, phosgene gas and neuropathology.