Exceptional Cure of a Patient with Progressive Advanced Squamous-Cell Lung Cancer after Selenite Treatment followed by Chemotherapy: A Case Report

Intravenous (i.v.) sodium selenite has been evaluated in patients with advanced cancer, but its potential clinical and biomarker-related effects remain incompletely understood. We report a patient with advanced squamous-cell lung cancer who was treated with high-dose intravenous sodium selenite within the SECAR phase I trial. The patient had recurrent, progressive disease after previous chemotherapy, radiotherapy, and targeted treatment, and no further standard treatment options were available. Sodium selenite was administered according to the study protocol and was followed by gemcitabine plus carboplatin. Imaging shortly after treatment showed stable disease; however, the patient subsequently improved clinically followed by gradual tumor regression. 2-[ 18 F]fluoro-2-deoxy- d -glucose positron emission tomography–computed tomography (FDG-PET/CT) performed in 2011 demonstrated no residual tumor, repeated bronchial and stent-related biopsies between 2014 and 2017 showed no malignancy, and available autopsy material 10 years after SECAR treatment showed no malignancy. Retrospective biomarker analyses showed strong membranous programmed death-ligand 1 (PD-L1) expression in the pretreatment tumor biopsy and a sustained decrease in plasma soluble programmed death-ligand 1 (sPD-L1) from 93 pg/mL before sodium selenite treatment to 70 pg/mL after treatment and 38 pg/mL at 12 weeks after completion of subsequent chemotherapy. This case describes an exceptional durable complete remission in a patient with advanced squamous-cell lung cancer after sodium selenite treatment followed by chemotherapy within a phase I trial. Although causality cannot be established from a single case, the approximately 10-year malignancy-free clinical course, repeated tumor-free bronchial biopsies, absence of malignancy in available autopsy material, and exploratory PD-L1/sPD-L1 findings support reporting this observation as hypothesis-generating. The case merits further investigation of sodium selenite in the treatment of PD-L1 expressing tumors. Trial Registration European Union Drug Regulating Authorities Clinical Trials Database (EudraCT) number 2006-004076-13.