Dear Editor,
We read with great interest the paper published in the International Journal of Surgery entitled: ‘The number of metastatic lymph nodes is more predictive of prognosis than location-based N stage for non-small cell lung cancer: a retrospective cohort study’1. The N classification in TNM was defined only by the anatomical location of metastatic lymph nodes (LN) since the fourth edition. The authors conducted a comprehensive cohort study to evaluate the prognostic performance of metastatic LN number in patients with non-small cell lung cancer (NSCLC). The study was not only conducted based on a large Chinese cohort but also had external validation from the SEER (Surveillance, Epidemiology, and End Results) database. The authors concluded that the number of metastatic LN has a significant prognostic value in the N descriptors.
In this study, the authors found a result that when comparing patients with the same number of metastatic lymph nodes (nN) group between the N1 and N2 groups in the Chinese cohort, the overall survival (OS) and the recurrence-free survival (RFS) were the same. These findings are consistent with the previous study2. Similar results were observed in the SEER cohort for OS and lung cancer-specific survival except for the N1–3 subgroup with a margin P value (P=0.049). However, further research is needed to determine if N1 and N2 patients in the same nN group have the same prognosis in terms of OS and RFS. With this conclusion, it would be necessary to conduct further evaluation to define the N classification between N1 and N2 patients based on both the anatomical location and the number of positive LN.
In the recent proposal for the revision of the N descriptors in the forthcoming 9th edition of the TNM classification for lung cancer, based on robust data and large intercontinental populations, the study suggests carrying forward the previous N0, N1, N2, and N3 descriptors. The N2 group was further subdivided into single-station involvement (N2a) and multiple-station involvement (N2b)3. In this cohort study, the authors divided patients with metastatic LN numbers into three groups based on the maximum χ 2 in X-tile (N[1–3], N[4–6], N>6). The survival curves showed clear differences for each group, which is in accordance with previous literature2,4,5. This conclusion indicates that the burden of nodal metastases is associated with prognosis. Further research may be needed to explore whether N2 patients should be subdivided into more groups.
Overall, we offer much appreciation to the authors for their contribution in presenting us with a comprehensive cohort study and providing strong support for the significant prognostic value of the number of metastatic lymph nodes in patients with lung cancer.
Ethical approval
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Consent
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Sources of funding
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Author contribution
L.-c.L. and Z.-y.P.: conceptualization and writing – original draft; J.-d.M.: conceptualization and writing – review and editing.
Conflicts of interest disclosure
There are no conflicts of interest.
Research registration unique identifying number (UIN)
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Guarantor
Jian-dong Mei.
Data availability statement
The datasets generated and/or analyzed during the current study are available from the corresponding author on reasonable request.
Provenance and peer review
Not applicable.
Footnotes
Assistance with the study: none.
Lin-chuan Liang and Zhi-yu Peng contributed equally to this work and are joint first authors.
Sponsorships or competing interests that may be relevant to content are disclosed at the end of this article.
Published online 4 December 2023
Contributor Information
Lin-chuan Liang, Email: linchuanliang129@126.com.
Zhi-yu Peng, Email: pengzy94@sina.com.
Jian-dong Mei, Email: jiandongmei@aliyun.com.
References
- 1. Xu L, Si H, Su H, et al. The number of metastatic lymph nodes is more predictive of prognosis than location-based N stage for non-small cell lung cancer: a retrospective cohort study. Int J Surg 2023; [Epub ahead of print]. [DOI] [PMC free article] [PubMed] [Google Scholar]
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Associated Data
This section collects any data citations, data availability statements, or supplementary materials included in this article.
Data Availability Statement
The datasets generated and/or analyzed during the current study are available from the corresponding author on reasonable request.