I recently was writing up some data about pCR after SBRT for lung and it still seems a bit of a surprise to folks that pCR rates increase over time after XRT. The velocity of this change over time is almost certainly related to histology and other factors like tumor doubling time. It's all about the...

I would probably manage this patient similarly to a patient who was being treated for anal canal cancer.  As long as the residual mass in the rectum continued to shrink with follow up, then I would not biopsy the mass unless there was a high index of suspicion that recurrent disease was present...

The approach to this patient would depend on the initial tumor extent and the dose of EBRT delivered. Where there perirectal/mesorectal nodes, and if so how many and how large? If it was known that the patient would be medically inoperable from the onset of therapy, I would consider dose escalation...