Watch and wait: Why, to whom and how.

The current standard of care for the treatment of locally advanced rectal cancer includes neoadjuvant chemoradiation (nCRT) followed by total mesorrectal excision (TME). The observation of significant primary tumor response to radiation and chemotherapy led to the idea of organ-preserving strategies in selected patients who achieved clinical, endoscopic and radiological evidence of complete tumor regression. One of these strategies includes no immediate surgery with close surveillance, known as the Watch and Wait strategy (W&W). The potential benefits of this approach with the avoidance of radical TME have to be weighed against the potential risk of local tumor regrowth. Exploration of these advantages and disadvantages will attempt to answer why W&W may be an attractive alternative to rectal cancer patients and their treating physicians. In order to safely implement this strategy, some key issues related to baseline staging, neoadjuvant treatment regimens, timing for tumor response assessment, must be carefully considered. The combination of these features will attempt to clarify "how" and "to whom" the W&W strategy may be considered. Ultimately, in the setting of contemporary neoadjuvant treatment regimens including total neoadjuvant therapy strategies (TNT), the achievement of a clinical complete response is likely to affect a significant proportion of patients. As endoscopic and radiological imaging modalities have evolved and improved, W&W is expected to become an integral part during multidisciplinary management decision. Finally, understanding the clinical consequences of local tumor regrowth both in terms of local and distant relapse may allow for optimal and safe selection of patients fully aware of advantages or disadvantages of this strategy.