Effect of the composite quality resection score for rectal cancer on oncological outcomes in a multicentre cohort study (CRONOS)

Abstract

Aim: Individual components of surgical quality in locally advanced rectal cancer (LARC) – circumferential and distal resection margins and mesorectal completeness – are known prognostic factors. However, their combined prognostic value as a composite score remains underexplored. This study aimed to evaluate the impact of a composite quality total mesorectal excision (TME) score on oncological outcomes, and how this effect may vary with intervals from neoadjuvant therapy (NAT) to surgery. Method: This retrospective, multicentre cohort study included patients with LARC treated between 2005 and 2020 across six referral centres in the CRONOS study. Patients were categorised by the composite quality TME (successful/unsuccessful) and by the NAT-to-TME interval: short (≤8 weeks), intermediate (>8 to ≤12), or long (>12). Primary outcomes were locoregional recurrence (LR), systemic recurrence (SR), and overall survival (OS) in the unsuccessful group. The interaction between the composite score and NAT-to-TME interval was assessed as a secondary outcome. Results: Of 1485 patients, 191 (12.9%) had an unsuccessful composite quality TME. This was significantly associated with increased risk of LR (HR 4.63, 95% CI: 3.04–7.05), SR (HR 2.10, 95% CI: 1.56–2.81), and reduced OS (HR 2.31, 95% CI: 1.79–2.98). Short and intermediate intervals increased the risk of LR in the unsuccessful group (pinteraction = 0.06). Conclusion: Patients with an unsuccessful composite quality TME are at high risk of recurrence and death. The link between shorter NAT-to-surgery intervals and poorer outcomes in this subgroup suggests that extending the interval beyond 12 weeks may help optimise results in selected patients.