Trial Protocol: Reaccumulation rate of pleural effusions after therapeutic aspiration: An observational cohort study to determine baseline factors associated with rate of pleural fluid reaccumulation following therapeutic aspiration in patients with malignant pleural effusion attending a pleural clinic (REPEAT).

Background: Malignant pleural effusion (MPE) is the build-up of pleural fluid in the space between the lung and chest wall due to advanced cancer. It is treated initially by large volume drainage (therapeutic aspiration). If the fluid reaccumulates, a definitive procedure is performed. There is wide variation in rate of reaccumulation. Patients with rapid reaccumulation often attend hospital as an emergency. Conversely, patients with slow reaccumulation do not need a definitive procedure and may experience cancelled or unnecessary procedures. This study aims to create and validate a multivariable prediction model to predict how quickly pleural fluid will reaccumulate in patients with MPE following therapeutic aspiration.

Research Question: Can we predict how quickly pleural fluid will reaccumulate in patients with MPEs?

Methods: A total of 200 patients with known or suspected MPE attending for therapeutic aspiration will be recruited from 5-10 UK hospitals over 20 months. Patients will be enrolled prior to undergoing aspiration. Following this, they will undergo chest X-ray, which will be repeated one week later (treatment as usual). Rate of reaccumulation will be calculated based on change of size of the effusion seen on X-ray. Data will be collected on common clinical biomarkers , size of effusion on pre-aspiration chest X-ray, volume of fluid drained. This data will be analysed to create a clinical score.A further validation cohort of 40 patients will be enrolled in parallel with creation of the score.

Anticipated Impact: The ability to predict rate of reaccumulation of MPE will enable patients and clinicians to make better informed treatment decisions. For patients with predicted rapid reaccumulation, a definitive procedure could be offered as first-line treatment, rather than a therapeutic aspiration. This will prevent emergency hospital admissions and decrease number of procedures. By contrast, patients whose effusions will recur slowly may avoid an unnecessary procedure.