Results of a prospective randomised control 6 vs 12 trial: Is greater tumour downstaging observed on post treatment MRI if surgery is delayed to 12-weeks versus 6-weeks after completion of neoadjuvant chemoradiotherapy?

Background

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.

Methods

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.

Results

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 

Conclusions

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

N/A

Funding

Biomedical Research Centre

Disclosure

All authors have declared no conflicts of interest.