Baseline tumour size is an independent prognostic factor for overall survival in PD-L1 ≥ 50% non-small cell lung cancer patients treated with first-line pembrolizumab

Background: Advanced non-small cell lung cancer (NSCLC) with a PD-L1 tumour proportion score ≥ 50% can be treated with pembrolizumab alone. Our aim was to assess the impact of baseline tumour size (BTS) on overall survival (OS) in NSCLC patients treated with pembrolizumab versus chemotherapy.

Methods: This retrospective, multicentre study included all patients with untreated advanced NSCLC receiving either pembrolizumab (PD-L1 ≥ 50%) or platinum-based chemotherapy (any PD-L1). The primary endpoint was the impact of BTS (defined as the sum of the dimensions of baseline target lesions according to RECIST v1.1 criteria) on OS.

Results: Between 09-2016 and 06-2020, 188 patients were included, 96 in the pembrolizumab (P-group) and 92 in the chemotherapy group (CT-group). The median follow-up was 26.9 months (range 0.13-37.91) and 44.4 months (range 0.23-48.62), respectively, while the median BTS was similar, 85.5 mm (IQR 57.2-113.2) and 86.0 mm (IQR 53.0-108.5), respectively (p = 0.42). The median P-group OS was 18.2 months [95% CI 12.2-not reached (NR)] for BTS > 86 mm versus NR (95% CI 27.2-NR) for BTS ≤ 86 mm (p = 0.0026). A high BTS was associated with a shorter OS in univariate analyses (p = 0.009) as well as after adjustment on confounding factors (HR 2.16, [95% CI 1.01-4.65], p = 0.048). The CT-group OS was not statistically different between low and high BTS patients, in univariate and multivariate analyses (p = 0.411).

Conclusions: After adjustment on major baseline clinical prognostic factors, BTS was an independent prognostic factor for OS in PD-L1 ≥ 50% advanced NSCLC patients treated first-line with pembrolizumab.