Increased number of negative lymph nodes is associated with improved cancer specific survival in pathological IIIB and IIIC rectal cancer treated with preoperative radiotherapy.

Qingguo Li,Sanjun Cai,Lei Liang,Guoxiang Cai,Dawei Li,Changhua Zhuo

doi:10.18632/oncotarget.2560

Abstract

Preoperative radiation significantly decreases the number of retrieved lymph nodes (LNs) in rectal cancer, but little is known with respect to the prognostic significance of negative LN (NLN) counts under these circumstances. In this study, Surveillance, Epidemiology, and End Results Program (SEER)-registered ypIII stage rectal cancer patients, and patients from Fudan University Shanghai Cancer Center (FDSCC) were combined and analyzed. The results showed that the survival rate of patients with n (cutoff) or more NLNs increased gradually when n ranged from two to nine. After n reached 10 or greater, survival rates were approximately equivalent. Furthermore, the optimal cutoff value of 10 was validated as an independent prognostic factor in stage ypIIIB and ypIIIC patients by both univariate and multivariate analysis (P < 0.001); the number of NLNs could also stratify the prognosis of ypN(+) patients in more detail. Patients in the FDSCC set validated these findings and confirmed that NLN count was not decreased in the good tumor regression group relative to the poor tumor regression group. These results suggest that NLN count is an independent prognostic factor for ypIIIB and ypIIIC rectal cancer patients, and, together with the number of positive LNs, this will provide better prognostic information than the number of positive LNs alone.

Highlights

Preoperative radiation following curative resection has become a standard method to treat locally advanced rectal cancer because of lowered local recurrence rates [1, 2]
These results suggest that negative LN (NLN) count is an independent prognostic factor for ypIIIB and ypIIIC rectal cancer patients, and, together with the number of positive lymph nodes (LNs), this will provide better prognostic information than the number of positive LNs alone
The proportion of high/moderate differentiation gradually decreased from ypIIIA to ypIIIC (74.9% to 59.6%), and the same phenomena was found with respect to histotype; the percentage of adenocarcinoma decreased from 90.6% in ypIIIA to 69.0% in ypIIIC

Summary

Introduction

Preoperative radiation (preop-RT) following curative resection has become a standard method to treat locally advanced rectal cancer because of lowered local recurrence rates [1, 2]. Patients with less than 12 LNs retrieved might have more favorable disease free survival rate than those with 12 or more LNs assessed [7, 11], but some studies continue to support the theory that identifying more LNs results in better survival [12, 13]. The total number of LNs (TLN) retrieved comprises both positive and negative LNs (NLNs), so the relationship between TLNs and prognosis is confounded by the prognostic effect of the number of positive LNs (PLNs). There is no research focusing on the correlation between NLN counts and patient prognosis in the setting of rectal cancer treated with preop-RT

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Results

Conclusion