Lymph node ratio is a powerful prognostic factor in patients receiving preoperative chemoradiotherapy for rectal cancer

Purpose. To evaluate whether lymph node ratio (LNR) is a prognostic factor in patient receiving preoperative chemoradiotherapy (pCRT) for rec- tal cancer. Patients and methods. A consecutive cohort of 308 patients (median age 62 years, M/F:202/106), who received pCRT from 2004 to 2007 within two Institutions, was evaluated. Clinical and histopathologi- cal data were prospectively recorded. Inclusion criterium was non metasta- tic mid-low locally advanced rectal cancer. LNR was defined as the num- ber of metastatic nodes divided by the number of total harvested nodes. A LNR of 0.18 was identified as the breakpoint for predicting overall sur- vival (OS). Based on this cut-off, patients were subdivided in: LNR-0 (ratio 0), LNR-1 (ratio: >0 to ≤ 0.18) and LNR-2 (>0.18). OS was calculated using the Kaplan-Meier method and a multivariate analysis was performed using the Cox’ model after stepwise selection. Results. In univariate analysis, variables that significantly affected OS were: distance of tumor from the anal verge (p=0.0003), type of resection (p=0.0253), pN (p=0.0402), total positive nodes (p=0.0023) and LNR (p=0.0052). In multivariate analysis, variables that independently affected OS were: distance of tumor from the anal verge with a RR (95%CI) of 0.834 (0.738-0.941) and p=0.003, and LNR with a RR (95% CI) of 0.421 (0.057-3.092) p=0.395 for LNR-1, and 2.413 (1.270-4.583) p=0.007 for LNR-2. Moreover, in 47 patients staged as pN1, LNR was able to discriminate two subgroups with a significantly (p=003) different prognosis: LNR-1 group (n=25, 5-year OS: 95%) and LNR-2 group (n=22, 5-yr OS: 53%). Conclusions. This study shows that, in patients receiving pCRT for rectal cancer, LNR is a strong prognostic factor, also able to discriminate subgroups with different prognosis in patients staged as pN1.