Renewed Response to Pembrolizumab After Salvage Radiotherapy for Oligoprogression in Advanced NSCLC: A Case Report

Immune checkpoint inhibitor (ICI) rechallenge may benefit selected patients with NSCLC, but the role of local radiotherapy for oligoprogression and late same-agent rechallenge remains uncertain. We report a patient with Stage IVA lung adenocarcinoma and a programmed death-ligand 1 tumour proportion score of ≥ 75% who achieved a durable partial response to first-line pembrolizumab. After isolated left supraclavicular nodal oligoprogression in 2020, he received salvage radiotherapy and remained off systemic treatment for almost 5 years. In late 2025, multiple new right lower lobe nodules and pleural-based lesions appeared near the original primary site and enlarged on serial CT, prompting pembrolizumab rechallenge. CT in February 2026 showed a renewed partial response. This case suggests that rechallenge with pembrolizumab may remain reasonable at late relapse in carefully selected patients with durable initial benefit, limited progression controlled locally, a long treatment-free interval, and good performance status.