Stage IIIA-N2 non-small cell lung cancer: could a new scoring system improve the management of heterogeneous disease?

We read with great interest the article by Nakagiri et al. [1] and colleagues reporting their long-term results in the surgical treatment of pathological stage IIIA-N2 non-small cell lung cancer (NSCLC). The Authors discuss on the clinical validity of the lymph node metastasis sub-classification, seeking in particular to analyze some pathological findings (involvement of the highest mediastinal lymph node or not; ‘skip’ vs. ‘non-skip’ N2-disease; ‘single N2’ vs. ‘multiple N2’; ‘single station N2’ vs. ‘multiple station N2’) that could have some potential impact on the survival. We completely concur with the statement that N2 disease is a mixture of heterogeneous prognostic subgroups, where different levels of involvement [it is appropriate to add also the number of lymph nodes invaded, lymph node ratio (invaded/total) [2] along with type of involvement (intra vs. extra capsular)] may indeed represent significantly different prognostic classes [3]. Despite this prognostic variability of the N2-disease, no revision was made according with the International Association for the Study of Lung Cancer (IASLC) analysis of the N-descriptors in the 7th edition of the TNM classification for lung cancer (‘there were insufficient data to determine whether the N-descriptors should be subdivided’)[4]. Probably, instead of analyzing each prognostic factor, the realization of a scoring system of the N2-status that takes into account all of these prognostic factors mentioned above would be more useful. This score may be obtained by the result of the retrospective analysis of large pathological data sets and the subsequent confirmation by specific prospective trials; of course the ultimate goal of this score could be the identification of prognostic classes (for example: N2a, N2b, N2c, etc.) in the clinical phase in order to facilitate the stage-dependent treatment planning and, consequently, the long-term outcomes of stage IIIa-N2. On the basis of these considerations, we warmly advocate further investigations of prognostic predictors in stage IIIa-N2 disease.

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