OC-006 Oncological outcome following ‘watch and wait’ for clinical complete response after pre-operative chemo-radiotherapy in patients with rectal cancer

Introduction In patients with rectal cancer, management by ‘watch and wait’ (W&W), with potential avoidance of surgical resection (SR), has emerged as a management option following a clinical complete response (cCR) after pre-operative chemoradiotherapy (CRT). However, precise quantification of oncological outcomes after this treatment pathway is unclear. Method Between 2010 and 2013, we followed a consecutive series of 259 patients with non-metastatic rectal cancer who completed pre-operative CRT (majority: 45 Gy in 25 daily fractions with concurrent fluoropyrimidine-based chemotherapy). Post-CRT, 31 patients (12%) were considered at a multi-disciplinary meeting to have cCR and offered W&W on a protocolised pathway. We supplemented these cases with a registry of 89 patients managed across four cancer treatment centres in the North West of England and North Wales (total cCRs: 120). Primary endpoint was actuarial rate of intraluminal re-growth. Secondary endpoints were non-intraluminal disease-free survival (niDFS) and colostomy-free survival (CFS). Comparisons with standard care (SR) were performed using propensity score matched-treatment analysis and using time-dependent survival analyses to account for differences in times to W&W decision and salvage SR. Results With a mean follow-up from WW and 3 underwent Papillon local radiotherapy. After propensity score matching, there were no deleterious effect on niDFS for patients treated by WW 0.269 to 1.174). However, there was a significant improvement in 3-year CFS rates for patients treated by W&W versus SR: 83% and 54% (log rank, p Conclusion Approximately two-thirds of patients with rectal cancer managed by W&W after cCR avoided surgical resection with improvement in colostomy-free survival, without loss of oncological safety. The outcomes from this multi-centred clinical cohort will assist the rectal cancer patient and oncologist with decision making at the outset of long-course CRT. This study was generously supported by the BDRF. Disclosure of interest None Declared.