Published online May 26, 2021. doi: 10.12998/wjcc.v9.i15.3531
Peer-review started: November 12, 2020
First decision: December 24, 2020
Revised: January 2, 2021
Accepted: March 10, 2021
Article in press: March 10, 2021
Published online: May 26, 2021
Processing time: 180 Days and 6.7 Hours
Rectal cancer (RC) is the world's fourth most deadly cancer with almost 900000 deaths annually. Therapy options for RC have been developed rapidly in the past decade, postoperative adjuvant radiotherapy and/or chemotherapy in high-risk patients can improve their long-term survival rates; however, the clinical outcomes among RC patients with the same tumor-node-metastasis (TNM) stage might be completely different. Unfortunately, due to the lack of reliable markers, selecting the optimal therapy for individuals is challenging for clinicians.
The degree of lymph node dissection (LND) is closely related to the prognosis of RC; however, so far, there is no objective and effective evaluation index for LND. Previous studies have suggested that examined lymph nodes (ELNs), negative lymph nodes (NLNs) and size were closely related to the prognosis of RC. Other studies have added another factor such as tumor size to improve the prognostic value of biomarkers, for example preoperative serum carcinoembryonic antigen (CEA) and prostate-specific antigen density. Therefore, we defined a novel prognostic score, the log odds of NLN/tumor size (LONS), as the log of the ratio between the NLN counts plus one and the tumor size, which reflects the NLNs adjusted by the tumor size, to better represent the degree of LND.
Our aim was to assess a potentially novel prognostic score to stratify risks for RC patients. At the same time, we also aimed to investigate whether LONS can distinguish different pathological stages and clinical features, to better guide the treatment strategies and follow-up plan.
The data of stage I–III RC patients were extracted from the Surveillance, Epidemiology, and End Results Program (SEER) database from 2004 to 2015. Univariate and multivariate Cox regression analyses were applied to determine the prognostic impact of the LONS. The optimal cutoff values of the LONS were calculated using the "X-tile" program. Stratified analysis of the LONS effect on cancer-specific survival (CSS) and overall survival (OS) were performed. The Kaplan-Meier method with the log-rank test was used to plot the survival curve and compare the survival data among the different groups.
In all, 41080 patients were finally included in the study and randomly divided into a training cohort (n = 28775, 70%) and a validation cohort (n = 12325, 30%). Univariate and multivariate analyses identified the continuous variable LONS as an independent prognostic factor for CSS and OS. The X-tile program indicated that the difference in CSS was the most significant for LONS of -0.8, and the cutoff value of -0.4 can further distinguish patients with a better prognosis in the high LONS group. Stratified analysis of the effect of the categorical variable LONS on CSS and OS revealed that LONS was also an independent predictor independent of pN stage, pT stage, TNM stage, site, age, sex, the number of ELNs, race, preoperative radiotherapy and CEA level.
Patients with high LONS have a better outcome than those with low LONS. LONS is an independent prognostic factor that is independent of clinicopathological features and can serve as a relative index for the degree of LND. LONS can be used as a novel marker for risk stratification and therapeutic decision-making in RC patients after surgery.
Due to the retrospective nature of the SEER database, we cannot obtain high-level clinical evidence, but our study provides a novel approach for the evaluation of LND and suggests a potentially novel prognostic score to stratify risks for RC patients at the same stage.