Abstract
PurposeThe oncologic impact of the lymph node (LN) regression level after preoperative chemoradiotherapy (PCRT) has not been thoroughly evaluated. Hence, this study aimed to examine whether the regression level of metastatic LNs following PCRT is associated with oncologic outcomes in rectal cancer.ResultsThe optimal number of cut points for LRG sum was determined to be three. The three LRG groups demonstrated different distributions according to the ypT and ypN stages (p < 0.001 for both). However, the distribution of the LRG groups was not associated with the TRG of the primary tumor (p = 0.527). The RFS significantly differed according to the LRG groups (p = 0.001). Moreover, the differences in RFS remained when the LRG groups were analyzed within each separate ypN stage. The LRG group was confirmed as a factor associated with RFS in the multivariate analysis (p=0.018), while the ypN stage was not (p=0.4).Patients and MethodsWe analyzed the outcomes of 142 rectal cancer patients diagnosed with ypN1 disease after PCRT followed by radical resection. The pathological responses of the primary tumor and LNs to PCRT were evaluated using the tumor regression grade (TRG) and LN regression grade (LRG), respectively. The impact of LRG on recurrence-free survival (RFS) was analyzed. The K-adaptive partitioning for survival data method was applied to determine the optimal number of cut points for the LRG-sum and the optimal number of subgroups.ConclusionThe LRG as an indicator of response to PCRT should be considered as a prognostic determinant in rectal cancer patients. Future large-scale prospective studies are needed to confirm this finding.
Highlights
The lymph nodes (LNs) regression grade (LRG) as an indicator of response to preoperative chemoradiotherapy (PCRT) should be considered as a prognostic determinant in rectal cancer patients
It has been established that the prognostic importance of metastatic lymph nodes (LNs) can be applied to both rectal cancer patients who have been treated with and without preoperative chemoradiotherapy (PCRT), there is still controversy on how to apply the pathological stage to the PCRT setting using data obtained in the non-PCRT setting
If future studies can confirm the relationship between the primary tumor and LN regression, this would be very helpful in terms of determining the pathological stage and prognosis, and for planning the subsequent surgical treatment following PCRT in certain rectal cancer patients
Summary
It has been established that the prognostic importance of metastatic lymph nodes (LNs) can be applied to both rectal cancer patients who have been treated with and without preoperative chemoradiotherapy (PCRT), there is still controversy on how to apply the pathological stage to the PCRT setting using data obtained in the non-PCRT setting. There are different perspectives regarding how to interpret the prognostic impact of metastatic LNs, especially in patients with primary tumors that demonstrate a good response to PCRT www.impactjournals.com/oncotarget [1,2,3]. This might be associated with the controversy whether we can evaluate LNs that fully comprise the metastatic foci in the same way as the LNs that consists of some the remaining metastatic foci, and whether the LNs without tumor foci from the beginning and LNs that no longer have tumor foci after complete regression should both be evaluated as N0. If future studies can confirm the relationship between the primary tumor and LN regression, this would be very helpful in terms of determining the pathological stage and prognosis, and for planning the subsequent surgical treatment following PCRT in certain rectal cancer patients
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