Neoadjuvant chemoradiation (CRT) for locally advanced rectal cancers induces tumor regression with size reduction (downsizing), in-depth penetration, and eventually lymph-node sterilization (downstaging): up to 25% of patients present complete pathological tumor regression with no residual disease at the time of surgery [63–69]. These patients are referred to as having a pathologic complete response (pCR). In a recent systematic review of 16 studies involving 1,263 patients with pCR, the finding of pCR was associated with a local recurrence rate of 0.7% and a distant metastasis rate of 8.7%. The 5-year overall survival rate was 90.2% and the disease-free survival rate was 87% [70].

Considering morbidity and mortality associated with rectal surgery, a nonoperative approach was first proposed to patients with complete tumor regression by Habr-Gama et al. [71]. This alternative strategy is described also as “organsparing treatment”, “rectal preservation”, or a “watch-and-wait” approach. In this setting, patients with apparent clinical complete response (cCR) to CRT are ideal candidates for the conservative approach. cCR is obviously less clearly defined than pCR and usually describes the absence of tumor based on a combination of clinical, radiologic, and endoscopic investigations. The landmark paper based on this policy was published by the Habr-Gama group in 2004 [71]. In the updated series published in 2011, 67 (39%) patients were considered to have cCR. At a mean follow-up of >5 years overall and disease-free survival in nonoperative patients were, respectively, 96% and 72% [72]. Similar results are reported by other, smaller, studies [73, 74], but these amazing results have not been repeated by others, who report an 80% relapse rate of complete clinical responders within 10 months of observation [75, 76].

This novel approach brings into question whether surveillance protocols following curative resection are appropriate in this particular patient subset. Again, the Habr-Gama group [77] suggests a strict follow-up program combining digital rectal examination, rigid proctoscopy with biopsy of suspicious lesions, and CEA levels every 1–2 months for the first year, every 6 months in the second year, and yearly thereafter. Chest X-ray and abdominal CT scans are recommended at 6 and 12 months and yearly thereafter. However, the real challenge of this novel approach remains to identify a true pCR without a resection.

Surveillance following colorectal cancer resection is intuitively beneficial and appealing. There is limited evidence of benefits in terms of earlier detection of recurrence, which results in more surgical resections with curative intent and improved overall survival. Controversy remains on the ideal surveillance methods and the frequency with which they should be applied. Under debate are the cost-effectiveness of various surveillance strategies and quality-of-life implications. In this era of cost containment, it is necessary to improve stratification of risk recurrence, identifying the patient population that will benefit from a value-based strategy and avoiding unnecessary examination in low-risk patients. It must be emphasized that the main purpose of a surveillance program is early identification of recurrence while curative interventions are still possible.