Has anyone else experienced the only identified cancer containing neck node that is decreasing steadily in response to treatment then begins to obviously, visually increase in size? The RO and MO both feel it is some kind of treatment response not disease spread or treatment failure. Said this can happen if there is a bleed near the node or other inflammatory responses in the node.

It's unusual for cancer to spread/increase during treatment, but It has happened to me, and was going to say it could be an inflammatory response, as I was told in my case, and was closely monitored. Radiation should shrink a tumor a certain percentage, and if that doesn't seem to occur, doctors can make certain decisions such watch and wait, change treatment or to do surgery. Also, radiation keeps working a number of weeks after treatment stops. One of mine was still enlarged, had two cancerous, that we waited 5 months after treatment to do a PET scan, which came back clear, at least that scan did. Others doctors may scan after 6 weeks when the usual wait time is 3 months or 12 weeks, so they can effectively deal with any reminiscent cancer, and have heard of scanning during treatment, but not sure if that was part of a clinical trial or reason the reason for scanning, such as one trial checking for tumor hypoxia by PET scan, and another type of infusion.