How does preoperative radiotherapy affect the rate of sphincter-sparing surgery in rectal cancer?

The use of preoperative radiotherapy has resulted in significant downstaging and downsizing of tumor, this in turn facilitated resections permitting sphincter preservation and coloanal anastomosis for patients who would otherwise have not been candidates for this type of surgery as concluded by some small studies. On the other hand, other clinical trials have shown that the effect of radiotherapy on the rate of sphincter preservation is still not clear. Moreover, different modes of radiotherapy have been tested on the rate of sphincter preservation such as pelvic irradiation with or without combination of chemotherapy, short or conventional course radiotherapy, and preoperative or postoperative radiotherapy with different timing intervals of surgery. Unfortunately, these trials didn't clearly answer the question of radiotherapy benefit for the sake of sphincter preserving of rectal cancer patients and the question remained hotly debated.