American scientists are working to develop a breath test capable of detecting lung cancer, even when the disease is in its early stages. The test will utilize a sensor capable of detecting chemical changes unique to the breath of individuals with lung cancer. As the patient breathes into the device, a series of colored dots, designed to change color upon chemically reacting with elements present in a lung cancer patient's breath, will produce what researchers have referred to as a "gas fingerprint for lung cancer." According to scientists from the Cleveland Clinic, the chemical reactions will occur because lung cancer cells emit chemicals, called volatile organic compounds or VOCs, which are then breathed out by those with the disease.
The test's ability to detect lung cancer in its early stages is significant because the disease is often silent and difficult to diagnose in these stages, the point at which it can be most effectively treated. Currently, the only test capable of early detection is a type of X-ray known as spiral computed tomography or CT, but the machines are expensive, require specially trained experts to interpret their results, and also pick up non-cancerous lesions that are costly and risky to test. In contrast, the breath test is inexpensive and easy to read by laypeople, because the spots on the sensor change color according to the chemicals with which they come in contact. In a study of 143 individuals, some with various types of lung cancer, some with other lung diseases such as emphysema, and some healthy, the test accurately predicted the presence of lung cancer in just under three out of four participants already known to have lung cancer. Lead researcher Dr. Pater Mazzone and his team say the breath test, if perfected, would be the most effective, inexpensive, non-invasive screening or diagnostic test for lung cancer, saving thousands of lives a year in the United States alone and revolutionizing the way cancer is detected. Last year, more than 174,000 Americans were diagnosed with lung cancer; of those 174,000, more than 160,000 died of the disease.


According to the passage, which of the following is true of volatile organic compounds?
They are the main cause of lung cancer.
They become cancerous when exposed to certain chemicals.
They constitute a "gas fingerprint for lung cancer."
They are present only in the early stages of lung cancer.
They cause the dots on the sensor to change color.