Pulmonary function tests (PFTs) are a group of non-invasive tests that assess how well the lungs work. These tests measure various aspects of lung performance, including lung volume, the rate of airflow, and the efficiency of gas exchange. The primary goal of PFTs is to evaluate lung function and help diagnose and manage certain lung disorders, such as asthma or chronic obstructive pulmonary disease (COPD). This article explores whether these functional assessments can detect lung cancer and clarifies their actual role in lung health and cancer care.
What a Pulmonary Function Test Measures
Pulmonary function tests are designed to quantify how effectively air moves into and out of the lungs and how well oxygen is absorbed into the bloodstream. Common components of a PFT include spirometry, lung volume measurements, and diffusion capacity tests. Spirometry, a frequently used test, measures the amount of air a person can exhale and how quickly that air is expelled.
Lung volume tests determine the total amount of air the lungs can hold at different points of inhalation and exhalation. These measurements include tidal volume (air breathed during normal breathing), vital capacity (total air exhaled after a maximal inhale), and residual volume (air remaining after maximal exhale). Diffusion capacity tests, such as the carbon monoxide diffusion capacity (DLCO), assess how efficiently oxygen and other gases transfer from the tiny air sacs in the lungs into the blood.
Why PFTs Do Not Detect Lung Cancer
Pulmonary function tests fundamentally measure the function of the lungs, assessing their mechanical capabilities and gas exchange efficiency. Lung cancer, however, is a disease characterized by the abnormal growth of cells that form tumors, representing a structural change within the lung tissue. PFTs are not designed to visualize or identify these cancerous growths directly. They cannot distinguish between a tumor and other conditions that might affect lung function, such as inflammation or other lung diseases.
While a large tumor might eventually impact lung function by obstructing airways or reducing lung capacity, PFTs would only indicate a general impairment, not the presence of cancer itself. The tests reveal how well the lungs are performing their duties, but they do not provide images or cellular information about the underlying cause of any functional decline. Therefore, PFT results cannot definitively diagnose lung cancer; they only highlight potential issues with lung performance.
How Lung Cancer is Detected
Detecting lung cancer primarily relies on imaging techniques and tissue analysis, which focus on identifying structural abnormalities and cancerous cells. A common initial step is a chest X-ray, which can reveal suspicious masses or changes in lung structure, though it cannot definitively diagnose cancer or detect small tumors. If an X-ray shows concerning findings, a computed tomography (CT) scan is typically performed next.
Low-dose CT (LDCT) scans are the only recommended screening test for lung cancer in high-risk individuals, as they can detect smaller tumors than X-rays. For a definitive diagnosis, a biopsy is necessary, involving the removal of a tissue sample for microscopic examination. Biopsies can be performed through various methods, including needle biopsies, bronchoscopy, or thoracoscopy. Positron emission tomography (PET) scans are also used, often in conjunction with CT (PET/CT), to help determine if cancer has spread to other parts of the body.
The Role of PFTs in Lung Cancer Care
While pulmonary function tests are not used to detect lung cancer, they play a meaningful role in the overall management of individuals diagnosed with the disease. PFTs are frequently performed before lung cancer surgery to assess a patient’s lung health and determine if they can tolerate the procedure. This assessment helps medical teams evaluate the potential risks of surgery, especially regarding safe tissue removal.
PFTs also serve to monitor lung health during and after cancer treatments. These treatments can affect lung function, and PFTs help detect treatment-related lung damage. Furthermore, PFTs are useful in diagnosing or managing other lung conditions that might coexist with lung cancer, ensuring a comprehensive approach to the patient’s respiratory well-being.