The presence of swollen lymph nodes in patients with idiopathic pulmonary fibrosis (IPF) at the time of their diagnosis can be a predictor of poor prognosis, associated with stronger disease severity and lower survival, a study suggests.
Patients with enlarged lymph nodes, specifically lymph nodes close to the lung, have mortality rates more than twice as high as those with normal-size lymph nodes. Lymph node enlargement may be a useful predictor to inform doctors and patients about the clinical course the disease is likely to take, and help decide early on about the most appropriate treatments.
The study, “Impact of mediastinal lymph node enlargement on the prognosis of idiopathic pulmonary fibrosis,” was published in the journal PLOS ONE.
One of the major obstacles in predicting the clinical course of IPF and response to therapy, as well as selecting the best available treatments for patients, is the lack of known, reliable prognostic factors.
Some studies have reported that the presence of swollen lymph nodes is commonly associated with IPF, affecting between 40% and 60% of patients, especially a type of lymph node close to the lung known as mediastinal.
Lymph nodes are part of a network of vessels and other tissues collectively called the lymphatic system, which is essential for the body’s ability to detect and get rid of viruses, bacteria, and other disease-causing agents before they can spread to other parts of the body.
Recent reports have supported a correlation between the remodeling of lymphatic vessels and a higher IPF incidence and more severe progression of lung fibrosis.
Changes in lymphatic vessels may lead to lymph node enlargement and can appear early after lung injury, triggering inflammation and contributing to the development of fibrosis.
With this association in mind, researchers wanted to determine if mediastinal lymph node swelling was related to IPF severity, and if it could be a useful factor for predicting disease outcome.
In the study, researchers retrospectively reviewed the medical registries of 132 IPF patients, with a median age of 72, who were enrolled at the Seoul National University Bundang Hospital in South Korea.
Data regarding initial lung function — including chest computational tomography (CT) scans — hospitalization, and survival were analyzed. In all patients, the degree of lung fibrosis and the presence of enlarged mediastinal lymph nodes were evaluated by chest CT scans, done within one year of diagnosis and evaluated independently by at least two radiologists.
Of the patients, 73 (55.3%) had enlarged mediastinal lymph nodes detected in chest CT scans, while 59 patients (44.7%) had none.
Patients with lymph node enlargement showed signs of poorer lung function and more severe fibrosis. They had significantly worse lung function parameters, namely a lower diffusing capacity for carbon monoxide (a test that assesses the lungs’ capacity to transfer oxygen from the air sacs into the blood) and more advanced Gender-Age-Physiology (GAP) stages, a disease staging system for IPF.
In addition, they also had worse lung fibrosis scores, as determined by CT scans.
Notably, the presence of swollen lymph nodes was found to be an independent predictor of higher mortality. The rate of death was 2.67 times higher in patients with altered lymph nodes than in those without. Reinforcing this correlation, the death rate of patients increased with the number of enlarged lymph nodes.
Other factors significantly associated with a poorer prognosis were older age, lower percentage predicted forced vital capacity — a measure of air flow in the lungs — more advanced GAP stages, and more severe fibrosis.
In addition, patients with enlarged lymph nodes tended to have more acute exacerbations and to require more frequent hospitalizations. Of those with swollen lymph nodes, 24.7% experienced acute exacerbations, and 43.8% were hospitalized due to respiratory reasons, compared with 16.9% and 40% of patients with normal lymph nodes.
Based on the results, the team concluded, “mediastinal LNE [lymph node enlargement] in IPF is associated with increased mortality and its occurrence may be considered a poor prognostic factor in patients with IPF.”
Lymph node enlargement “is a very useful baseline factor that can easily be obtained through chest CT at the time of diagnosis” the researchers said. As such, their presence “as well as the number of LNs [lymph nodes] showing enlargement can be used for risk stratification.”