Would 45 Gy to the pelvis be sufficient for a locally advanced rectal cancer that has a complete metabolic response to TNT?  

If you define the standard of care as what the vast majority of people do, the standard of care is to give 50.4 Gy in 28#, especially if nonoperative management is the goal. If surgery is part of the plan, we found that preoperative chemoradiation to 45 Gy followed by mesorectal excision resulted in...

If the goal is watchful waiting, I would not alter the dose based on initial chemotherapy response. I would advocate for treating above 50.4 Gy (often, 54-56 Gy are used) in the WW scenario to the area of initial disease, and 45/50 if TME is planned. Our minimum 'high dose' boost volume is generall...