Lymph node harvest and survival in rectal cancer

Abstract

4048 Background: The NCCN recommends that at least 12 nodes be identified in a colon cancer specimen to ensure adequate staging. This standard is applied to rectal cancer despite anatomic and treatment differences. The factors that predict adequate nodal harvest and the relationship between harvest and survival in rectal cancer patients, with or without preop xrt are unknown. Methods: We performed a retrospective cohort study of 8,580 patients with stage I-III rectal cancer undergoing proctectomy from 1996–2004 using SEER-Medicare. Multivariate logistic regression was performed to identify patient and hospital variables associated with adequate LN harvest. Kaplan-Meier curves and Cox regression compared survival among patients who had ≥12, 1–11, or no nodes harvested, adjusting for patient and hospital characteristics. Results: 28% of patients had ≥12 nodes and 14% had no nodes harvested. Patients who were older, had more comorbidities or underwent preop XRT or emergent surgery were less likely to have ≥12 nodes harvested. High surgical volume and teaching status were positively associated with having ≥12 nodes harvested. Median survival by nodal harvest by stage and treatment are shown in table 1. After multivariate adjustment, node status remained significantly associated with mortality (p<0.001). Compared to patients with no nodes harvested, patients with 1–11 nodes were 27% (HR 0.73) and patients with ≥12 nodes 40% (HR 0.63) less likely to die. The effect of node harvest varied by stage and treatment, with the weakest association with survival in patients with stage III disease and stage I patients who received preop XRT or postop therapy. Conclusion: Nodal harvest is associated with survival following proctectomy for rectal cancer, primarily in Stage I and II patients. Further research is needed to understand the contribution of treatment and quality measures to this finding and to determine whether number of nodes is an appropriate quality measure for patients who undergo preop XRT. Median Survival (Years) # Nodes Surgery Only Preop XRT, Surgery Surgery, Postop Tx I II III I II III I II III 0 5.9 1.4 5.1 3.9 4.4 3.3 1–11 7.6 3.6 1.8 7.7 5.4 3.4 6.0 6.1 4.9 ≥12 9.3 4.8 2.1 6.3 7.2 3.1 6.1 8.4 4.9 P-value <.001 <.001 .08 .02 .005 .49 .04 <.001 .78 No significant financial relationships to disclose.