People who have lung cancer often have fluid removed from the chest cavity because the disease causes fluid to accumulate there, according to Healthline. The membrane surrounding the lung, called the pleura, normally has a small amount of fluid to keep the lungs moist.
Cancer treatments such as radiation therapy or chemotherapy sometimes lead to fluid buildup, or pleural effusion, Healthline states. Typically extra fluid is drained from the around the lungs through a needle or small tube placed into the chest. If the fluid returns, other treatments are needed. For instance, after the fluid is removed, a substance, usually talc, is introduced into the chest cavity to help the pleura stop leaking.