Lower GI 2017

What is the mechanism of effect of preoperative CRT?

1. To prevent local recurrence by treating microscopic areas not seen and so not routinely removed by surgeon (discontinuous deposits etc ? 2. To prevent local recurrence by treating areas not routinely removed by surgeon (external iliac nodes/obturator nodes etc..) ? 3. To prevent local recurrence by countering spillage ie rendering cells non-viable with RT? 4. To prevent local recurrence by countering spillage growing ie tumour bed effect? 5. To prevent local recurrence by compensating for poor surgical technique? 6. To prevent local recurrence by immune effects?