Deferral of rectal surgery following a continued response to preoperative chemoradiotherapy (Watch and Wait) study: A phase II multicenter study in the United Kingdom.

Abstract

489 Background: Neoadjuvant chemoradiotherapy (CRT) and surgical resection are standard components of therapy for patients locally advanced rectal cancer (T3,T4 or N+) in UK. In 15%-30% of patients treated pre-operatively with CRT will develop pathological complete response (CR). The time from completion of CRT to maximal tumour response is as yet unknown. This study is the first prospective study to attempt to identify the percentage of patients who can safely omit surgery and the safety of deferred surgery in patients who achieve clinical complete response post CRT. Of the 59 patients required for the study, this provides an update on 19 patients entered. Methods: Patients with locally advanced rectal cancer requiring neoadjuvant treatment are identified in the multidisciplinary meet (MDT). Patients undergo CRT using a minimum of 50.4Gy in 28 # daily conformal CT planned CRT with concomitant Capecitabine at 825mg/m2 BD. MRI pelvis and body CT are repeated 4 weeks post CRT and rediscussed at MDT. If there is a good partial response or CR, patients are considered for Deferral of Surgery Study. Based on the pre treatment clinical staging, patients are considered for adjuvant chemotherapy as per NICE guidance. At any point of the study, if there is histology proven tumour regrowth or progression, patient undergo surgery. Results: 10 (53%) patients remain in CR. 6 (32%) patients underwent surgical resection with clear margin after detection of tumour regrowth at from 2-23 months post CRT. 5 out of 6 of the patients with tumour regrowth underwent PET CT as per protocol, and all tumour regrowth in those 5 patients were detected by PET CT, i.e. FDG avid disease. The pathological stages on these 6 patients were ypT2N0 CRM negative in 5 and ypT3N0 CRM negative in 1. 3 (15%) patients with tumour regrowth refused surgery. Conclusions: In the 19 recruited patients, all the patients with tumour regrowth underwent surgical resection with clear margins. PET CT appears a useful tool for detecting tumour regrowth. The median time for tumour regrowth is 17.5 months post CRT. The trial will be successful if at least 11/59 patients are able to safely omit surgery. Accrual of patients continues. No significant financial relationships to disclose.