The prognostic significance of the ratio of positive to total nodes in colorectal cancer

Abstract

4045 Background: Patients with node positive colorectal cancer (CRC) have a grave prognosis. Current AJCC staging distinguishes between those with 1–3 positive lymph nodes (N1) and those with 4 or more (N2). We sought to determine whether the ratio of positive to total nodes examined (LNR) was a more powerful predictor of outcome than N staging. Methods: 2,636 patients diagnosed between January 1, 1994 to December 31, 2003 with stage III CRC from Region 5 of the California Cancer Registry were analyzed. LNR was stratified into quintiles of <0.19, 0.2–0.39, 0.4–0.59, 0.6–0.70 or 0.8–1.0. The major endpoint was actuarial 5-year disease specific survival (DSS). Significant differences in DSS between groups were determined by the log-rank test. A multivariate Cox proportional hazard regression was performed for all patients to determine whether N stage, LNR, number of lymph nodes examined, or number of positive lymph nodes were independent prognostic factors. Results: The median age was 71 with women making up 49.9% of the patients. 65% of the patients (n=1,717) had N1 disease; and 35% had N2 disease (n=919). 5 year DSS among N1 and N2 disease was 65% and 47%, respectively (p<0.0001). Within the N1 group, increasing LNR quintiles had worsening 5 year DSS of 71%, 63%, 59%, 52% and 50% (p<0.0001). Similarly for the N2 group, 5 year DSS worsened with increasing LNR quintiles: 74%, 53%, 52%, 43%, and 31% (p<0.0001). Absolute difference in DSS between the highest and lowest quintiles for N1 was 21%; and N2, 43%. Multivariate analysis revealed that the number of nodes examined (p=0.0116), number of positive lymph nodes (p=0.0002), N stage (p=0.0139) and LNR (p=0.017) were all predictors of DSS. Quintiles 4 (RR=1.39, 95% CI=1.0087–1.9253) and 5 (RR=1.72, 95% CI=1.2406–2.4004) were more powerful predictors of DSS than N stage (RR=1.2613, 95% CI=1.0478–1.5184) or number of positive lymph nodes (RR=1.0457, 95% CI=1.0223–1.0698). Conclusions: LNR along with number of lymph nodes examined and number of positive lymph nodes is a predictor of DSS in stage III patients. Furthermore, a LNR ≥ 0.6 (quintiles 4 and 5) is a stronger prognosticator than N stage or number of positive lymph nodes. No significant financial relationships to disclose.