Watch-and-Wait as a Therapeutic Strategy in Rectal Cancer

Abstract

Purpose of review: Pathological complete response is seen in approximately one fifth of rectal cancer patients following neoadjuvant chemoradiation. Since these patients have excellent oncological outcomes, there has been a rapidly growing interest in organ preservation for those who develop a clinical complete response. We review the watch-and-wait strategy and focus on all aspects of this hot topic, including who should be considered for this approach, how should we identify treatment response and what are the expected outcomes.

Recent findings: The major challenges in interpreting the data on watch-and-wait are the significant heterogeneity of patients selected for this approach and of methods employed to identify them. The evidence available comes mostly from retrospective cohort studies, but has shown good oncological outcomes, including the rate of successful salvage surgery, locoregional control and overall survival.

Summary: There is currently not enough and not robust enough evidence to support watch-and-wait as a standard approach, outside a clinical trial, for patients achieving clinical complete response following neoadjuvant chemoradiation. Furthermore, there is a lack of data on long-term outcomes. However, the results we have so far are promising, and there is therefore an urgent need for randomised control studies such as the TRIGGER trial to confirm the safety of this strategy.

Keywords: Complete response; Deferral of surgery; Non-operative management; Organ preservation; Rectal cancer; Watch and wait.

Fig. 1

Rectal cancer management at the Royal Marsden Hospital

Fig. 2

Maintained complete response of a rectal tumour, 4 years following chemoradiation. A typical appearance scar is visible, with no evidence of tumour recurrence

Fig. 3

Low rectal tumour before treatment with full invasion of the muscularis at 4–8 o’clock position. The tumour borders the intersphincteric plane, therefore the CRM is involved at the level of the distal levators (a). Post CRT MRI demonstrates an area of low signal fibrosis at the site of the treated tumour, and no evidence of macroscopic residual intermediate signal suggestive of tumour—mrTRG2 (b)

Fig. 4

Low rectal tumour before treatment, infiltrating the rectal wall at 5–10 o’clock position with evidence of spread beyond the muscularis and spread into the intersphincteric plane, with invasion of the right levator (a). On post CRT MRI, the treated tumour demonstrates intermediate signal predominantly suggestive of macroscopic residual disease—mrTRG4 (b)

Fig. 5

TRIGGER trial flowchart (summary). Further details are available in the protocol, including chemoradiotherapy regimen, chemotherapy agents and number of cycles