ABSTRACT
Herein, we report a case of a 73-year-old female patient diagnosed with cT4N0M1a lung adenocarcinoma with KRAS G12C mutation, PDL1 < 1% and treated in fourth-line setting with gemcitabine after progression under nivolumab. After one infusion of gemcitabine, the patient presented with an acute worsening of general condition (performance status 4) with extensive skin lesions and fever, leading to hospitalization and diagnosis of acute generalized exanthematous pustulosis. Initial blood work revealed multiple organ failures with an important inflammatory syndrome. Patient state improved after intravenous hydration and local and systemic corticosteroids. The decision was made to stop systemic cancer treatment. Two months follow-up showed a remarkable response on all cancer localizations. Although immunotherapy is transforming cancer care, predicting response to immunotherapy remains challenging and resistant mechanisms remain mostly unknown. This case underlines that important immune-stimulation can lead to tumor response in a patient previously refractory to all antitumor treatments.