I am not sure how much interest there is, but let me throw it out anyway.
I am noticing a very interesting phenonoma where I see lots of patient exhibit what I call an refractory state within each stage. While many do go from stage 1 thru 4, a small percent of people goes into a refractory state but does not progess to the next sage. This is especially more prevelent in Stage 2 patients, where they do not advane to stage 3 but stay at stage 2 . no matter what you do, they stay there. This is most difficult, as the patient becomes frustrated. They hit the "plateau" and stay there. Fortunately I have been quite successful in getting them out of this refractory state. This state has yet to be explored by any research. I am just sharing my experiene from a clinical front line perspective since this is a discussion about staging.