Objective: This study aimed to assess the impact of the number of metastatic lymph nodes (LNs) on survival and propose a subdivision of the N2b category in colorectal cancer (CRC) patients.Methods: We retrospectively analyzed from two sources: clinicopathologic data of CRC patients with stage pTxN2bM0 who initially underwent radical surgery at Cancer Hospital, Chinese Academy of Medical Sciences/National Cancer center (NCC), and patients with stage pTxN0-2bM0-1 in the Surveillance, Epidemiology and End Results (SEER) database from January 2010 to December 2015. The optimal cutoff value of the number of positive lymph nodes (PLNs) was determined based on the principle of maximum chi-square value. We constructed survival curves using the Kaplan–Meier method, assessed survival differences with the log-rank test, and conducted univariate and multivariate analyses using the Cox proportional hazard regression model.Results: A total of 68,335 CRC patients were included: 240 from the NCC cohort, and 68,095 from the SEER cohort. Within the SEER cohort, 65,189 patients had M0 stage disease and 2,906 had M1 stage disease. The optimal PLN cutoff value determined by X-tile software (Version 3.6.1) was 13. According to PLN, stage N2b patients were divided into two groups: stage N2b# (7 ≤ PLN < 13) and stage N3 (PLN ≥ 13). In the NCC cohort, the 5-year overall survival (OS) rates of stage N2b# and N3 patients were 66.0% and 45.7%, respectively (p< 0.001). In the SEER cohort, the 5-year cancer-specific survival (CSS) rate was 57.1% for stage N2b# patients compared with 40.2% for stage N3 patients (p< 0.001). The results of multivariate Cox analysis demonstrated that modified stage pN was the independent prognosis factor of OS in the NCC cohort (HR = 1.869, 95%CI:1.253–2.787,p= 0.002); modified stage pN was also the independent prognosis indicator of CSS in the SEER cohort (N3:N0, HR = 8.170, 95%CI: 7.298–9.146,p< 0.001). There was no survival difference between TxN3M0 and TxN0-2b#M0 (5-year CSS rate: 40.2% vs. 30.1%,p= 0.050; 5-year OS rate: 35.3% vs. 27.8%,p= 0.358).Conclusions: The N category served as a strong independent prognostic indicator in CRC patients. Furthermore, PLN emerged as an independent prognostic factor specifically in stage N2b CRC patients. These findings suggest that clinicians may utilize PLN for prognostic stratification and tailor adjuvant therapeutic strategies accordingly for patients diagnosed with stage N2b CRC.
目的：本研究旨在评估转移性淋巴结（LNs）数量对结直肠癌（CRC）患者生存的影响，并提出对N2b亚类的进一步细分。 方法：我们回顾性分析了两组数据：来自中国医学科学院肿瘤医院/国家癌症中心（NCC）初次接受根治性手术的pTxN2bM0期CRC患者的临床病理资料，以及2010年1月至2015年12月监测、流行病学和最终结果（SEER）数据库中pTxN0-2bM0-1期患者资料。根据最大卡方值原则确定阳性淋巴结（PLNs）数量的最佳截断值。采用Kaplan-Meier法绘制生存曲线，Log-rank检验评估生存差异，并使用Cox比例风险回归模型进行单因素和多因素分析。 结果：共纳入68,335例CRC患者：NCC队列240例，SEER队列68,095例。SEER队列中，65,189例为M0期，2,906例为M1期。通过X-tile软件（3.6.1版）确定的PLN最佳截断值为13枚。根据PLN数量，将N2b期患者分为两组：N2b#期（7 ≤ PLN < 13）和N3期（PLN ≥ 13）。在NCC队列中，N2b#期和N3期患者的5年总生存（OS）率分别为66.0%和45.7%（p < 0.001）。在SEER队列中，N2b#期患者的5年癌症特异性生存（CSS）率为57.1%，而N3期患者为40.2%（p < 0.001）。多因素Cox分析结果显示，修正的pN分期是NCC队列中OS的独立预后因素（HR = 1.869，95%CI：1.253–2.787，p = 0.002）；在SEER队列中，修正的pN分期也是CSS的独立预后指标（N3:N0，HR = 8.170，95%CI：7.298–9.146，p < 0.001）。TxN3M0与TxN0-2b#M0期患者间生存率无显著差异（5年CSS率：40.2% vs. 30.1%，p = 0.050；5年OS率：35.3% vs. 27.8%，p = 0.358）。 结论：N分期是CRC患者强有力的独立预后指标。此外，PLN数量是N2b期CRC患者特异的独立预后因素。这些发现提示临床医生可利用PLN数量对N2b期CRC患者进行预后分层，并据此制定个体化辅助治疗策略。
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