The optimum interval between CRT and surgery for locally advanced rectal cancer remains controversial. If greater downstaging occurs with a longer interval to surgery, this may impact on rates of sphincter preservation and survival. A prospective, randomised, multicentre trial was undertaken to determine whether greater rectal cancer downstaging and regression occurs when surgery is delayed to 12 compared to 6-weeks.
The primary endpoint was difference in proportion of patients in each arm downstaged according to MRI T-stage - defined as any reduction in T-stage/sub-stage. A sample size of 218 patients was required. Secondary endpoints included pCR and mrTRG 1-2 rates.
A total of 237 patients were randomised: 122 (51%) into the 6-week and 115 (49%) to the 12-week arm. A significantly greater proportion downstaged in the 12-week (58%) compared with 43% in the 6-week arm (p = 0.019). The pCR rate was 9% in the 6-week versus 20% for the 12-week arm (p
Waiting 12-weeks after CRT results in significantly more mrT downstaging, pCR and improved mrTRG. Since mrTRG is a validated predictor of disease free survival, undertaking surgery before maximal regression may be disadvantageous.
Clinical trial identification
Legal entity responsible for the study
Biomedical Research Centre
All authors have declared no conflicts of interest.