Lymph node yield after rectal resection is a predictor of survival among patients with node-negative rectal adenocarcinoma.

Background: Pathologic review of at least 12 lymph nodes is recommended by the American Joint Committee on Cancer following surgical resection of rectal cancer. However, implications of lymph node yield on prognosis are unclear. This study evaluates the impact of lymph node yield on survival among pathologic node-negative patients who received appropriate neoadjuvant chemoradiation.

Methods: The National Cancer Database from 2010 to 2016 was queried for clinical stage II and III rectal adenocarcinoma with neoadjuvant chemoradiation, resection of the primary tumor, negative surgical margins, and pN0M0 pathologic stage. Data were analyzed with χ, student's t test, or Mann-Whitney U test as appropriate. Propensity score matching controlled for clinicodemographic variation. Survival was estimated with Kaplan-Meier curves and Cox hazards analysis.

Results: Inadequate lymph node yield (1-11 nodes on pathology) led to a 29% increased risk of mortality compared to adequate lymph node yield (≥12 nodes on pathology). Among patients with an incomplete pathologic complete response to neoadjuvant therapy, 5-year survival was estimated to be 73% for inadequate lymph node yield and 78% for adequate lymph node yield (P = .002). Among patients with a complete pathologic response, 5-year survival estimated to be 82% for inadequate lymph node yield and 90% for adequate lymph node yield (P = .006). Among patients with inadequate lymph node yield and complete pathologic response, 5-year survival improved with the use of adjuvant chemotherapy (90.4%), compared to those without adjuvant chemotherapy (78.5%, P < .001).

Conclusion: These findings suggest an inadequate lymph node yield can negatively impact survival, despite negative nodal status and a pathologic complete response to neoadjuvant therapy.