Would you offer additional radiation in a young patient with T4N1 rectal cancer, s/p TNT and pelvic exenteration with a positive deep margin without gross disease seen on post-operative imaging?

This is a very difficult decision. Although somewhat arbitrary, it is considered desirable to have at least a 6-month interval, preferably a year, before considering re-irradiation. For a patient who had surgery following TNT, the interval since the first course of radiation is presumably only a few months, which would argue against re-irradiation. However, if two conditions could be met, I would consider retreatment. I would want to work with the surgeon to determine whether it is possible to identify the specific area where the positive margin is likely to be located, as I would consider radiating a small volume, but not a second pelvic field. A related consideration is that I would consider re-treatment if there is no small bowel within ...