A malignant pleural effusion is defined by the accumulation of fluid in the presence of malignant cells or tumor tissue in the pleural space. Malignant pleural effusions are common, affecting approximately 15% of patients with malignancies, and account for more than 125,000 hospitalizations in the United States annually, with estimated healthcare costs of greater than $5 billion per year.1,2 The incidence of malignant pleural effusions is expected to rise as a result of the increasing global cancer prevalence and development of more effective systemic therapies.3 The presence of a malignant pleural effusion is a hallmark of advanced-stage disease and denotes a poor overall prognosis, with a median survival ranging between 3 and 12 months depending on the primary tumor type.4 Although some patients may be asymptomatic, the majority develop dyspnea at rest with associated reduced quality of life.5 Despite advancements in understanding the pathophysiology of malignant pleural effusions and remarkable progress in cancer treatments over the last decade, management strategies for malignant pleural effusions remain palliative, with the goal of relieving patient symptoms and minimizing the need for repeat invasive procedures.
Although any malignancy may involve the pleura, epithelial malignancies account for approximately 80% of malignant pleural effusions, with lung and breast cancer representing the majority of cases (Table 77-1). Lung cancer is the leading cause of a malignant pleural effusion, which is present in an estimated 15% of lung cancer patients at diagnosis and develops in up to 50% of patients during the course of their disease. Effusions can occur with any lung cancer histology but are most frequent in adenocarcinomas.6,7 Breast cancer is the second leading cause of a malignant pleural effusion. Approximately 7% to 11% of breast cancer patients will develop a malignant effusion, and these effusions are typically unilateral and ipsilateral to the primary tumor site.8–10 Other carcinomas that commonly cause malignant pleural effusions include malignancies of gastrointestinal and ovarian origin. Lymphomas, including both Hodgkin and non-Hodgkin lymphomas, are the most common hematologic malignancies associated with malignant pleural effusions and account for approximately 7% to 16% of all cytologically confirmed malignant pleural effusions.11,12 Patients with a malignant pleural effusion due to lymphoma typically have mediastinal lymph node involvement.13 The primary origin of the tumor is not identified in approximately 10% of malignant effusions.2,11 Malignant mesothelioma is the most common primary pleural tumor to cause a malignant pleural effusion; the incidence varies by geographic region and is highly correlated with exposure to asbestos.
TABLE 77-1Most Common Primary Malignancies Among Patients with a Malignant Pleural Effusion (n = 126,825) ||Download (.pdf) TABLE 77-1 Most Common Primary Malignancies Among Patients with a Malignant Pleural Effusion (n = 126,825)