Several single-centre studies investigated whether the number of metastatic lymph nodes would be a relevant supplementary prognostic factor in pathological N1 (pN1) non-small cell lung cancer (NSCLC), however, with conflicting results. The aim of this study was to determine the prognostic impact of the number of metastatic N1 lymph nodes in different histological subtypes for patients with stage II-N1 NSCLC.
We performed a retrospective cohort study using data from the Netherlands Cancer Registry, including patients treated with a surgical resection for stage II-N1 NSCLC in 2010–2016. Overall survival (OS) was compared between patients with single (pN1a) versus multiple (pN1b) metastatic pN1 nodes. With a multivariable analysis we evaluated the impact of the number of metastatic pN1 nodes in different histological subtypes.
The series involved 871 (67%) patients with pN1a and 438 (33%) with pN1b NSCLC. 5-year OS was 53% for pN1a versus 51% for pN1b. 54.1% of patients with pN1a and 54.8% of patients with pN1b received adjuvant chemotherapy. In multivariable analysis, the difference between pN1b and pN1a was statistically significant, but small (HR 1.19, 95% CI 1.01–1.40). Furthermore, histological subtype, age, pathological T stage, and adjuvant chemotherapy were independent prognostic factors. When stratifying for histological subtype, the prognostic impact of pN1a/b was only observed in adenocarcinoma patients (HR 1.44, 95% CI 1.15–1.81). Beneficial effects of adjuvant chemotherapy were not different for pN1a versus pN1b.
The number of metastatic pN1 nodes was associated with a minor difference in survival and its impact was limited to adenocarcinoma histology. Biological parameters such as histological subtype may be more appropriate for inclusion in future TNM revisions and may guide the use of new (neo)adjuvant systemic therapies.
Legal entity responsible for the study
Has not received any funding.
A. de Langen: Research grant/Funding (self): BMS; Research grant/Funding (self): MSD; Research grant/Funding (self): AstraZeneca; Non-remunerated activity/ies, Non-financial support: Merck; Research grant/Funding (self): Boehringer Ingelheim; Non-remunerated activity/ies, Non-financial support: Roche. All other authors have declared no conflicts of interest.