Defining Volume Thresholds for Colorectal Cancer Surgery Using Stratum Specific Likelihood Ratios

Higher procedure volume correlates with improved surgical outcomes, yet recent literature has questioned whether this relationship persists in modern times. Reports of an attenuated volume-outcome association may reflect the limitations of a single, static, cutoff rather than true weakening of the underlying relationships. Stratum-specific likelihood ratios generate multiple empirically derived volume strata that may detect persistent gradients that are obscured by binary threshold approaches.

(1) To define hospital-level volume thresholds for colorectal cancer resections using stratum-specific likelihood ratios, (2) assess these thresholds across multiple outcome measures, procedure types, and tumor locations, and (3) examine whether the volume-outcome relationships persist across temporal cohorts.

Retrospective cohort study.

National Cancer Database from 2004-2020.

Patients undergoing colorectal resection for cancer. Patients with metastatic disease were excluded.

Primary outcome was 90-day mortality. Secondary outcomes included 30-day mortality and textbook outcome (length of stay ≤7 days, negative surgical margin, survival >90 days, and no 30-day readmission).

Overall, 1,052,875 patients underwent colorectal resection at 1344 hospitals. Stratum-specific likelihood ratios identified 6 volume strata (≤42, 43-70, 71-108, 109-280, 281-439, and ≥440 colorectal resections per year) with progressively decreasing 90-day mortality across groups (≤42: 5.9% to ≥440: 0.6%). The threshold of 71 resections per year was identified as the optimal threshold. Consistent gradients were also observed across 30-day mortality and textbook outcome and persisted across procedure types and tumor locations. Volume-outcome associations remained significant across all temporal cohorts, including the most recent period (2016-2020; p <0.001).

Limited to Commission on Cancer facilities, lacks granular hospital characteristics, restricted to malignant indications.

Stratum-specific likelihood ratios reveal persistent volume-outcome associations for colorectal cancer resections across multiple strata, even in contemporary data. These findings suggest that the reports of an attenuated volume-outcome relationship may reflect limitations of a single, static volume cutoff, rather than weakening of this association. See Video Abstract.