EP2006 - Impact of Neoadjuvant Chemotherapy on Lymph Node Harvest and Postoperative Outcomes Following Colectomy for Colon Cancer: A National Cohort Study

Purpose/Background: The role of neoadjuvant chemotherapy (NAC) in colon cancer is still poorly defined. While NAC may downstage tumors and improve systemic control, its influence on surgical outcomes is less clear. This study aimed to evaluate the impact of NAC on lymph node harvest and short-term postoperative outcomes following colectomy for colon cancer.

Methods/Interventions: Using the American College of Surgeons National Surgical Quality Improvement Program (ACS-NSQIP) database, we identified patients >18 years of age who underwent colectomy for colon cancer between 2010-2023. Patients were categorized by receipt of NAC versus surgery-first management. The outcomes were total lymph node harvest and 30-day postoperative mortality, morbidity, readmission, unplanned return to the operating room, prolonged ileus, and anastomotic leak. Multivariable logistic regression models were constructed to estimate adjusted odds ratios (ORs) for outcomes, after controlling for demographics, comorbidities, and ASA class. Analyses were repeated within each cancer stage (0-IV).

Results/Outcomes: Among 124,932 patients, 11.7% received NAC. NAC recipients were younger (median 59 vs 68 years) and more often male (59% vs 51%). Across all stages, the mean number of lymph nodes evaluated were significantly lower after NAC (18.57; 95% CI: 18.41, 18.73) compared with surgery-first (21.84; 95% CI: 21.77, 21.90). This difference persisted across all stages, with the largest absolute reduction in Stages II and III. In the adjusted model, NAC was independently associated with a 3.6 node reduction in mean nodal yield (-3.63; 95% CI: -4.40 to -2.86).

Across all stages, NAC was also associated with higher adjusted odds of overall postoperative morbidity (OR 1.65, 95% CI 1.47-1.86), readmission (OR 1.92, 1.66-2.22), prolonged ileus (OR 1.83, 1.60-2.09), and anastomotic leak (OR 1.52, 1.20-1.92), without significant differences in 30-day mortality (OR 1.27, 0.72-2.26) and unplanned return to the operating room (OR 1.23, 0.98-1.54). Stage-specific analysis revealed similar trends. For Stage III, NAC increased the odds of postoperative morbidity (OR 1.53, 1.25-1.88), readmission (OR 2.05, 1.60-2.63), prolonged ileus (OR 2.04, 1.62-2.57), and anastomotic leak (OR 1.90, 1.27-2.83). While in Stage IV, NAC was associated with higher overall morbidity (OR 1.54, 1.15-2.05) and prolonged ileus (OR 1.48, 1.06-2.06).

Conclusion/Discussion: In this large national cohort, neoadjuvant chemotherapy prior to colectomy for colon cancer was associated with a modest but significant reduction in lymph node harvest and higher postoperative morbidity compared with surgery-first management. Recognizing the impact of neoadjuvant therapy on nodal yield is essential for accurate pathologic staging and treatment planning. Future prospective studies should explore whether minimum nodal thresholds should be adjusted for patients receiving NAC. Furthermore, additional studies are warranted to identify patient subgroups that derive the greatest oncologic benefit from neoadjuvant chemotherapy while minimizing surgical risk.

Mean Lymph Node Harvest Based on Stage
Model-Adjusted Odds Ratios of Outcomes, Full Cohort