Despite the decline in cigarette smoking over the last 50 years, lung cancer remains the most common cause of cancer related death in the United States. In patients at the highest risk for lung cancer, a recent large study showed that an annual low radiation dose CT (LDCT) of the chest could decrease the number of deaths by 20 percent. The test has now been recommended by the US Preventive Services Task Force (USPSTF) and the Centers for Medicare & Medicaid Services (CMS) for people age 55-80 (age 55-74 for CMS) who have smoked the equivalent of at least 1 pack per day for 30 years, and who are actively smoking or have quit within the last 15 years.
Positive results are common
Many people have small lung nodules (“spots”) visible on chest CT, even if they do not have notable symptoms. CT screening detects a lot of these nodules that would otherwise go unnoticed. These spots can be due to a current or prior infection, environmental exposures, autoimmune diseases, or other causes of inflammation. A small proportion of them will be due to cancer. In the largest trial to date, nearly 40 percent of the participants had a nodule over 4mm in size during one of the three annual exams. Of these positive studies, a cancer was diagnosed in only 4 percent. Positive results are common, most often these prove not to be cancer.
Some nodules have more concerning features
Every case is unique; reviewing the case with a health care provider familiar with lung cancer screening is important. In general, the most important features of nodules that suggest cancer are size and growth. Lung nodules under 4-6mm (about ¼ inch) are unlikely to be cancer and may not require any additional testing outside of the annual CT scan. Nodules that are noted to be “calcified” are typically not cancerous and may not require additional testing as well. “Non-calcified” nodules greater than 6mm or those showing growth between scans generally require more evaluation.
Further testing may be recommended
Depending on the appearance, size, and growth pattern of the nodule, further testing may be pursued. In many circumstances, the nodule will be followed over time with low-radiation dose CT scans at 3-6 month intervals. If there is no growth for 2 years (longer for some types of nodule) the nodule is not likely to be cancer. If the nodule has more concerning features, a scan called a PET/CT may be considered. Alternatively, a biopsy may be recommended. Biopsies can often be done using a series of CT scans to guide a biopsy needle to the nodule. In some situations, the biopsy may be done with bronchoscopy, where the biopsy is done from inside the lung.
Lung cancer screening at the University of Vermont Medical Center
If you smoke now or have in the past, ask your healthcare provider if lung cancer screening is right for you. Screening tests are currently being performed at the University of Vermont Medical Center. A dedicated Lung Nodule Clinic and the Lung Cancer Multidisciplinary Clinic are available to see people who have had a positive result on a CT screening study.
Garth Garrison, MD, is a pulmonary disease physician at The University of Vermont Medical Center and an assistant professor at the Larner College of Medicine at UVM.