P1.18-10 The Prognostic Impact of the Extent of Nodal Involvement in NSCLC Treated with Radical Chemoradiation

Abstract

There is inconclusive evidence that single station N2 disease has better prognosis compared to multi-level N2 or N3 involvement in NSCLC. We aimed to evaluate the prognostic impact of the extent and location of nodal involvement in NSCLC treated with radical chemoradiation (CRT). We retrospectively evaluated patients treated with radical CRT between 2007-2015 in a single tertiary institution. Nodal staging was based on imaging (CT/PET) and/or endoscopic/surgical evaluation. Nodal involvement was categorised as N0, N1, single station N2 (N2single), multi-level N2 (N2multi), ipsilateral N3 SCF (N3scf) and contralateral mediastinal/SCF N3 (N3contra). Single station N2 was further divided into one or >1 nodal deposits. Overall survival (OS) and disease-free survival (DFS) were defined from the date of radiation commencement to the date of death and relapse, respectively. Cox regression and Kaplan-Meier methods were used for survival analysis. A total of 207 patients were included, with 165 (80%) treated with concurrent and 42 (20%) with sequential CRT. Most tumours were adenocarcinomas (55%: EGFR+ 26%, EGFR- 49%, unknown 25%) followed by SCC (36%) and other subtypes (9%). Clinical nodal staging was as follows: N0=8%, N1=7%, N2single=19%, N2multi=37%, N3scf=12% and N3contra=16%. Conventional AJCC nodal staging was not prognostic of OS (p=0.4) or PFS (p=0.4). However, patients with N2single (median OS=40 months) and N3scf (median OS=55 months) had improved OS compared to N2multi (median OS=23 months) and N3contra (median=20 months) (p=0.005) (Figure 1). In the N2single subset, those with single nodal deposit had longer median OS (44 months) compared to >1 nodal deposits (27 months) but this was not statistically significant, likely due to the small number of patients (p=0.4). There was no significant difference in DFS between nodal groups, although N2single and N3scf showed a trend towards longer PFS compared to N2multi and N3contra (p=0.09). In multivariate analysis, N2multi (HR 1.71, 95% CI 1.08-2.71, p=0.02), T4 (HR 2.02, 95% CI 1.12-3.65, p=0.02) and older age (HR 1.03, 95% CI 1.01-1.05, p=0.003) were associated with inferior OS but not the use of sequential CRT (HR 1.31, 95% CI 0.86-1.99, p=0.2). In this study, N2single and N3scf stage III NSCLC showed improved overall survival compared to N2multi and N3contra disease after CRT. These findings suggest that nodal distribution, rather than conventional AJCC nodal staging, may have a greater prognostic impact in NSCLC treated with CRT.