The Stephenson nomogram, which predicts the outcome of salvage radiation, has been revalidated: http://www.ncbi.nlm.nih.gov/pubmed/19466946 .
The electronic version, a calculator, can be found here:
The updated paper version of the nomogram is here, but I find the digital version much easier.
The upshot of the validation is that the nomogram is a good rough guide to probability of success. It's better at the two ends of the risk spectrum (high and low) than it is for men in the middle, however.