Rectal cancer surgery, even by gold standard total mesorectal resection (TME), is invasive and carries a risk of complications and morbidities. With the adoption of neoadjuvant chemoradiotherapy, a watchful waiting (WW) approach has been proposed for patients with a clinical complete response (cCR) in order to delay or entirely avoid surgery. The initial results with this strategy have been promising, but new data from a retrospective study from the Memorial Sloan Kettering Cancer Center (New York, USA) raise concerns.

This case-series involved 113 patients with a cCR to neoadjuvant therapy who were subsequently managed through WW. Twenty-two of these patients had local regrowths, all of which were detected through routine surveillance (72% within 1 year of cCR), with 20 patients (91%) having pelvic disease control after salvage surgery. Notably, however, patients with local relapse had a markedly higher risk of distant metastasis (36% vs 1%; P < 0.001). Moreover, no pelvic recurrences occurred in a control group comprising 136 patients who underwent TME and had a confirmed pathological complete response to neoadjuvant therapy, and only 5 (4%) of these patients developed metastases.

These differences in oncological control were reflected in the survival data. At 5 years, disease-free survival was 75% in the WW group versus 92% in the control group, disease-specific survival was 90% versus 98% and overall survival was 73% versus 94%.

One must be cognizant, however, of the selection and recall biases that are inherent in retrospective studies. Of note, patients in the WW group were older (median age of 67.2 years versus 57.3 years; P < 0.001) and had cancers located closer to the anal verge (median 5.5 cm versus 7.0 cm), which might reflect differences in tumour biology.

Perhaps improved approaches to patient selection for WW are required that ensure a very low risk of recurrence. Importantly, the risks of WW should be weighed against the benefits of organ preservation and reduced morbidity. Notwithstanding, randomized clinical trials are needed to clarify the role of WW in patients with rectal cancer.