Background: Decreased number of recovered nodes is a poor prognostic factor in rectal cancer and may reflect quality of surgery and inadequate sampling of nodes leading to significant understaging of patients. Neoadjuvant CRT seems to contribute to a decrease in the number of recovered nodes after radical surgery and therefore, the least number of nodes required to minimize underestimation of disease staging is undetermined. The purpose of this study was to determine the influence of the total number of nodes recovered on the risk of finding node metastases for advanced rectal cancer following neoadjuvant CRT.
Methods: Patients with non-metastatic distal rectal cancer who underwent neoadjuvant CRT (50.4Gy and 5FU/Leucovorin) followed by radical surgery (TME) were eligible for the study. All patients with ypT3-4 rectal cancer managed by neoadjuvant CRT and radical surgery were retrospectively reviewed in order to determine a correlation between the number of recovered nodes and the risk of lymph node metastases and the critical number nodes associated with significant underestimation of nodal spread and disease staging.
Results: 435 patients with distal rectal cancer managed by neoadjuvant CRT were included in the study. Overall, 165 patients had ypT3-4 rectal cancer after radical surgery and TME. The median number of recovered nodes was 9 nodes/patient. Patients with >9 nodes/specimen were at increased risk for N+ disease (47% vs 27%; p=0.01). Less than 6 nodes/specimen was associated with significant decreased risk of finding node metastases (p=0.006: Sensitivity 82% and Specificity 39%).
Conclusions: A minimum of 6 nodes/specimen is required to provide proper nodal staging in ypT3-4 rectal cancer after neoadjuvant CRT and radical surgery. Less than 6 lymph nodes/specimen in patients with ypT3-4 rectal cancer managed by neoadjuvant CRT and TME should be considered at increased risk for disease stage underestimation.