Microscopic N2 disease exhibits a better prognosis in resected non-small-cell lung cancer

The management of pIIIA-N2 non-small-cell lung cancer (NSCLC) is still controversial. In particular, there are wide variations in overall survival (OS), suggesting the existence of subgroups among N2 patients. We aimed to evaluate the prognostic value of microscopic pN2 in NSCLC.

Between 1996 and 2015, the data from all 982 pathologically stage IIIA-N2 patients who underwent surgery with curative intent for NSCLC were retrospectively reviewed. Microscopic pN2 disease was defined as a nodal metastasis ranging from 0.2 to 2 mm in size.

With a median follow-up of 17 months (2-101), the 5-year OS for the whole cohort was 31%. Microscopic N2 was observed in 309 (31.5%) patients. Microscopic N2 was associated with better median OS compared with macroscopic N2 [42 months (95% CI 36.85-47.15) vs 23 months (95% CI 19.7-26.29), P < 0.0001, with a corresponding 5-year OS rate of 39 and 21%, respectively]. In multivariate analysis, microscopic N2 remained a favourable independent prognostic factor [HR 0.681 (95% CI 0.481-0.967), P = 0.03]. The median OS of microscopic N2 patients who benefitted from simple follow-up was significantly better than those who underwent chemotherapy, radiation therapy or both [43 months (95% CI 24.22-61.78) vs 22 months (95% CI 17.43-26.47) vs 31 months (95% CI 27.66-34.34) vs 16 months (95% CI 14.6-17.4), P = 0.008].

Microscopic N2 seems to be associated with better prognosis in patients with pIIIA-N2 NSCLC and these could benefit from a simple follow-up. Prospective cohort studies are necessary to confirm these preliminary results.