Results of the STRATIFY study (Staging by Thoracoscopy in potentially radically treatable Lung Cancer associated with Minimal Pleural Effusion)

<bold>Introduction:</bold> In retrospective studies, minimal pleural effusion (mini-PE) is associated with recurrence following radical treatment of lung cancer, suggesting occult pleural metastases (OPM) in up to 70%. Mini-PE is defined as an ipsilateral effusion which is cytology negative or too small to aspirate. STRATIFY prospectively evaluated thoracoscopic staging in mini-PE for the first time. <bold>Methods:</bold> STRATIFY was a prospective multicentre observational study (7 UK centres, Jan 2020-May 2024, target n=50). The primary objective was to determine OPM prevalence in patients with otherwise radically-treatable lung cancer. Secondary objectives included technical feasibility, safety and impact on treatment plans. Inclusion criteria were (1) suspected/confirmed stage I-III lung cancer (2) Mini-PE (3) PS 0-2 (4) Radical treatment feasible if OPM excluded (5) ≥16 years (6) informed consent. Exclusion criteria included any metastatic disease or contraindication to the chosen thoracoscopy method. Local Anaesthetic Thoracoscopy (LAT) was preferred but VATS was allowed. <bold>Results:</bold> 27/37 screened patients were recruited (24 LAT; 3 VATS); 54% target sample size. Mean age was 69 (1.7) years. Thoracoscopy was completed in 96% LAT and all VATS cases. The prevalence of OPM was only 14% (95% CI 4.2-33.7%). There were 2 adverse events (AEs) across all cases and no serious AEs. Overall stage was changed in 5/27 (19%). Treatment plan changed in 8/27 (30%). <bold>Conclusion:</bold> Despite reduced precision due to below-target recruitment, the prevalence of OPM was significantly lower than suggested by retrospective series. Staging LAT was technically feasible, safe and clinically useful.