I realize this is a controversial question, but no I would not. There is no way to know if the cells present at the margin are clonogenicly viable or not. If you look at the results of the Dutch TME trial and the MRC CO 7 trials, patients with positive margin after short course radiation had around ...

I agree with @Christopher H. Crane. The additional challenge is often knowing exactly where that positive margin was. Under close observation, it is likely you will find any local recurrence very early, and be able to more aggressively treat a much smaller volume, with the added advantage of additio...