Validation of the Proposed cN2 Subclassification in the Eighth Edition of the IASLC Staging System: A Prospective Phase II Multicenter Study

INTRODUCTION: Surgery for N2 stage IIIA NSCLC is not recommended in major guidelines. Nevertheless, it has been noted that single-station N2 may have a better prognosis than multistation N2 and that surgery can be performed as the main therapeutic option. METHODS: We conducted a prospective phase II study for single-station clinical N2 (cN2) NSCLC to evaluate the efficacy and safety of surgical resection without induction therapy. Complete resection with lobectomy, bilobectomy, or pneumonectomy followed by ipsilateral mediastinal lymphadenectomy was performed in 32 of 34 enrolled patients, whereas the remaining two patients underwent incomplete resection. Three-quarters of the patients underwent subsequent adjuvant chemotherapy. RESULTS: The 5-year overall survival rate was 58.5% (95% confidence interval: 41.9–75.4) for all 34 patients, and eight patients (23.5%) with pN0 or pN1 seemed to have been enrolled. The 5-year overall survival rates for single-station cN2 without and with hilar node enlargement were 81.3% and 37.5%, respectively (p = 0.025). Surgical mortality was 0% for all, and no considerable perioperative complications were noted; however, two patients died of interstitial pneumonia and unknown cause within 3 months after surgical resection. CONCLUSIONS: This is the very first prospective study on the surgical approach for cN2 NSCLC, and our result partially validated the proposed classification of the N descriptor in the new staging system. The treatment for single-station cN2 without hilar node enlargement would better if it were similar to that for cN1 disease. Induction chemotherapy or chemoradiotherapy may not be needed for such an entity.