The CHHiP (Conventional or Hypofractionated High-dose Intensity Modulated Radiotherapy In Prostate Cancer) trial investigated hypofractionated radiotherapy for localised prostate cancer. Forward or inverse-planned intensity-modulated techniques were permitted. A total of 337 participants were involved in this study. The patients were identified by prostate and rectal volumes and on radiotherapy dose for comparisons of toxicity. The IP patients had smaller volumes of rectum irradiated to 50–70Gy. FP patients were found to have smaller volumes of bladder irradiated to 74Gy. Acute grade two and bowel toxicity was found to be even worse with FP,with no significant differences in acute urinary toxicity. At two years, RTOG grade two plus bowel toxicity rates were IP 2/53 and FP 0/53. Whereas, for RTOG grade two plus bladder rates were 1/57 and 0/54 for IP and FP respectively.
Vast differences were found between dose–volume histograms from both FP and IP methods. There were some associations between DVH differences and normal tissue effects, which were statistically significant for acute bowel toxicity and for minor levels of toxicity using LENT/SOM and RMH late side-effect bowel subscales favouring IP techniques. On the contrary, IP techniques were associated with an excess of grade one bladder side-effects. In conclusion, both IP and FP techniques were associated with low levels of late tissue toxicity.