Impact of severe postoperative complications on oncologic outcomes after curative resection for stage I–III colorectal cancer: a multicenter study

BACKGROUND: Severe postoperative complications (Clavien-Dindo [CD] grade ≥ 3) may compromise long-term oncologic outcomes after colorectal cancer (CRC) surgery, but their impact across all pathological stages remains unclear. METHODS: We retrospectively analyzed 1990 patients who underwent curative resection for pStage I-III CRC at six hospitals (2016-2021). Multivariable Cox proportional hazards models were used to evaluate recurrence-free survival (RFS), overall survival (OS), cancer-specific survival (CSS), and time to recurrence (TTR). Stratified analyses were performed by pathological stage and complication type (intra-abdominal infectious complications [IAI] vs. non-IAI), and a 30-day landmark analysis was conducted. RESULTS: CD ≥3 complications occurred in 128 patients (6.4%). On multivariable analysis, CD ≥3 complications were independent adverse prognostic factors for RFS (hazard ratio [HR] 1.84, P < .001), OS (HR 2.52, P < .001), and CSS (HR 2.04, P = .024), but not for TTR (HR 1.22, P = .451). Stage-stratified analyses showed significant associations with worse RFS and OS in pStage II-III, with trends in pStage I. CSS was significantly worse in pStage III (HR 3.06, P < .001). TTR showed no significant association with CD ≥3 complications in any pStage. IAI complications were independently associated with worse CSS (HR 2.21, P = .039), whereas non-IAI complications were not. These adverse effects persisted after 30-day landmark analysis. CONCLUSIONS: CD ≥3 complications independently worsen RFS, OS, and CSS but do not significantly affect TTR after curative resection for pStage I-III CRC. IAI complications are particularly associated with worse cancer-specific mortality. This discordance suggests that severe complications may not primarily accelerate recurrence itself, but may instead impair survival after recurrence, highlighting possible mechanisms beyond direct recurrence acceleration.