Rectal Tumor Height and Neoadjuvant Therapy Inform Interpretation of the Conventional Twelve-Node Benchmark: A...

The twelve-node benchmark is widely used as a minimum reference for staging adequacy and quality assessment after colorectal cancer resection. This study evaluated whether rectal tumor height and neoadjuvant therapy (NAT) status should be considered when interpreting this benchmark in rectal cancer.

This single-center retrospective cohort study included patients with non-metastatic colorectal adenocarcinoma who underwent minimally invasive radical resection with evaluable lymph node counts between 1 June 2019 and 30 June 2024. Rectal cancer constituted the primary analytic cohort; a contemporaneous colon cancer cohort was included as an institutional reference. The primary outcome was low lymph node yield (LNY), defined as fewer than twelve retrieved lymph nodes; lymph node yield (LNY) as a count outcome was analyzed as a complementary outcome. We first performed descriptive comparisons across tumor-height and NAT strata. We then fitted multivariable-adjusted negative binomial and logistic regression models in the rectal cancer cohort, including tumor height, NAT status, and their interaction to estimate adjusted height- and NAT-associated contrasts and test interaction.

The cohort included 4282 patients: 2317 with colon cancer and 1965 with rectal cancer, including 1024 without NAT and 941 with NAT. The colon cancer cohort had a median LNY of 19; the interquartile range (IQR) was 14-26, and the low-yield rate was 8.9%. Rectal cancer without and with NAT each had a median LNY of 15.0 (IQR, 12.0-19.0) and low-yield rates of 17.4% and 21.6%, respectively. Within rectal cancer, low-yield classification increased from high to mid to low rectal tumors (13.5%, 20.4%, and 26.8%). In adjusted rectal interaction models, comparisons with high rectal tumors were estimated at the no-NAT reference level. Low rectal tumors were associated with lower LNY (incidence rate ratio (IRR), 0.83; 95% CI, 0.77-0.89; p < 0.001). They also had higher odds of low LNY (odds ratio (OR), 2.20; 95% CI, 1.44-3.35; p < 0.001). In the mid-rectal stratum, NAT was associated with higher odds of low LNY (OR, 1.82; 95% CI, 1.24-2.66; p = 0.002); however, the overall interaction for low LNY was not statistically significant (p for interaction = 0.331).

The twelve-node benchmark remains a useful reference for pathological staging and quality review. In the studied minimally invasive, sphincter-preserving rectal cancer cohort, a lymph node count below twelve should be interpreted together with tumor height, NAT exposure, and treatment composition rather than being used as an isolated indicator of inadequate surgical or pathological quality.