A malignant pleural effusion (MPE) is the accumulation of fluid containing cancer cells in the pleural space. This space is the thin area between the two layers of the pleura, membranes that line the lungs and the inside of the chest cavity. Normally, this space contains a small amount of fluid that acts as a lubricant. MPE is not a cancer itself, but a complication of an existing cancer that has spread, disrupting the normal fluid balance and causing it to build up.
Underlying Causes and Symptoms
MPE develops when cancer cells migrate to the pleura from a tumor elsewhere in the body, traveling through the bloodstream or lymphatic system. They can also spread by direct invasion from a nearby tumor. Once in the pleural space, these cells can block the lymphatic vessels responsible for draining pleural fluid. This blockage, combined with increased fluid production stimulated by the cancer, leads to accumulation.
Lung and breast cancer account for a majority of MPE cases. Other cancers frequently associated with the condition include:
- Lymphoma
- Ovarian cancer
- Stomach cancer
- Colon cancer
- Mesothelioma (a cancer of the pleura itself)
The fluid buildup exerts pressure on the lung, preventing it from fully expanding and causing shortness of breath (dyspnea), which can occur at rest and often worsens with activity. Patients may also experience a persistent dry cough, chest pain, or a feeling of heaviness in the chest. The pain is often a dull ache but can be sharp and worsen with deep breaths. General symptoms like fatigue and unexplained weight loss may also be present, reflecting the advanced nature of the cancer.
The Diagnostic Process
Confirming a diagnosis begins with imaging tests. A chest X-ray is often the first step and can reveal fluid in the pleural space. For a more detailed view, a computed tomography (CT) scan can provide more information on the fluid’s location and extent, and identify any pleural nodules or thickening. These imaging studies visualize the effusion but cannot definitively confirm cancer cells.
To confirm the diagnosis, a thoracentesis is performed. This procedure involves inserting a thin, ultrasound-guided needle through the chest wall to withdraw a sample of the fluid. Thoracentesis serves two purposes: it provides a fluid sample for laboratory analysis and can offer immediate symptom relief by draining the excess fluid.
The collected fluid is sent to a lab for cytological examination, where a pathologist looks for malignant cells under a microscope. If cancer cells are found, the MPE diagnosis is confirmed. If the initial analysis is inconclusive, a pleural biopsy may be necessary. This involves removing a small piece of pleural tissue for examination, either with a needle or through a minimally invasive surgery called thoracoscopy.
Treatment Approaches
Treatment for MPE is primarily focused on relieving symptoms and improving quality of life, and is considered a palliative measure. The most direct approach is a therapeutic thoracentesis, which drains fluid to alleviate shortness of breath and discomfort. While this provides immediate relief, the fluid often reaccumulates, sometimes within days or weeks, necessitating repeat procedures.
For patients with rapid fluid reaccumulation, an indwelling pleural catheter (IPC) may be recommended. An IPC is a thin, flexible tube inserted into the pleural space that remains in place, with one end exiting the skin. This allows the patient or a caregiver to drain the fluid regularly at home, avoiding repeated hospital visits and providing greater symptom control.
Pleurodesis is another option for managing recurrent effusions. This procedure prevents fluid buildup by causing the two layers of the pleura to stick together, eliminating the pleural space. After the fluid is drained, a chemical irritant like talc is introduced into the space, causing inflammation that leads to scarring and adhesion of the pleural membranes. This option is considered for patients whose lung can fully re-expand after drainage.
In addition to procedural interventions, treating the underlying cancer with systemic therapies can also help control the effusion. Treatments like chemotherapy, targeted therapy, or immunotherapy can shrink the tumor and reduce cancer cells in the pleural space, slowing fluid production. The choice of treatment depends on the primary cancer’s type and stage, and the patient’s overall health and preferences.
Prognosis and Palliative Care
The development of an MPE indicates the cancer has reached an advanced stage, and the prognosis is often limited. Life expectancy after an MPE diagnosis varies significantly depending on the primary cancer type, the extent of the disease, and the patient’s health and response to treatment. Because of this variability, specific survival statistics are best discussed with a healthcare provider.
The focus of care for patients with MPE is on palliative measures aimed at maximizing comfort and quality of life. Palliative care is a specialized field of medicine providing an extra layer of support for patients with serious illnesses. It is not limited to end-of-life care and can be provided alongside curative treatments to manage distressing symptoms like pain and fatigue.
This approach also addresses the emotional, psychological, and social challenges of a cancer diagnosis. The team, which may include doctors, nurses, and social workers, provides support for both the patient and their family. The goal is to help the patient live as well as possible by focusing on their individual needs and preferences.