Do New pN Subclassifications Proposed by IASLC’s Lung Cancer Staging Project Agree with ypN Categories after Trimodality Therapy for Initial N2 Disease?

Abstract

IntroductionThe International Association for the Study of Lung Cancer's lung cancer staging project has recently proposed a new subclassification of pN1-2 based on multiplicity of involved nodal stations and presence of skip metastasis. The authors investigated whether this new subclassification agrees with the ypN categories after trimodality therapy for initially N2 disease. MethodsFrom March 2001 until June 2014, trimodality therapy consisting of preoperative thoracic radiation therapy concurrent with weekly platinum-based doublet chemotherapy and surgical resection was successfully undertaken in 508 patients after histopathologic confirmation of N2 disease. Data on 481 patients were analyzed and compared with special focus on the current and new pN classification. ResultsThe median duration of overall survival (OS) was 58 months, and the 5-year OS rate of all patients was 48.8%: 62.6% in ypN0; 45.5% in ypN1; 37.6% in ypN2; and 0% in ypN3. Comparisons between neighboring ypN categories showed significant difference between ypN0 and ypN1 (p = 0.028) but not between other categories. The 5-year OS rates according to new ypN subclassification were 48.2% in ypN1a, 39.0% in ypN1b, 52.8% in ypN2a1, 37.9% in ypN2a2, and 32.1% in ypN2b. Although the OS rate of ypN2a1 was numerically higher than those of ypN1b and ypN2b, comparisons between neighboring ypN categories revealed no significant difference. ConclusionsThe current study was specifically intended to investigate whether ypN categories after trimodality therapy agree with International Association for the Study of Lung Cancer's new pN subclassification. Through the current study, the authors have confirmed that ypN downstaging to ypN0-1 from initial N2 stage is a favorable factor with respect to OS and raised the need for refinement of ypN subcategorization after trimodality therapy.