Screening and Diagnosis of Lung Nodules
Pulmonary (lung) nodules are detected by chest X-ray or CT scan performed for purposes other than lung cancer screening in patient with no known history of cancer.
Prior to this year, lung nodules were followed with surveillance CT scans at three to six month intervals until no changes had been observed for two years, and the nodules were then classified as benign. This approach did not take into account low risk patients who were less than 35 years-old, nonsmokers, and without previous history of cancer. Latest research shows no benefit to such frequent imaging in this group of patients. When indicated, providers may order additional tests to further characterize these nodules.
Computed Tomography scan (CT scan)
CT scans, including low-dose spiral CT scans, are used to provide information about nodules including size, growth rate, and morphology. In recent years, CT scans have become so advanced as to detect nodules as small as one to two mm in diameter. In a CT screening trial by the Mayo Clinic it was reported that less than one percent of nodules less than five mm in patients without previous cancer history were malignant. Further research found that in following nodules less than five mm, no delay in diagnosis was made by obtaining follow up CT study in 12 months, as opposed to the traditional three to six months.
Positron Emission Tomograph (PET)
PET scans detect metabolically active cells (cells that are actively reproducing), such as cancer cells. To perform a PET scan, a tracer is used, usually 18 F-fluoro-2-deoxy-glucose (FDG). This radioactive sugar is injected into the bloodstream. Metabolically active cells take up the sugar. The PET scan takes pictures and areas of increased metabolism are highlighted.
The sensitivity of a PET scan decreases significantly in nodules less than seven to eight mm. It is most accurate for lesions at least one cm in size. The PET scan is a helpful tool not only for assessing metabolic activity of a lesion, but for helping rule disease elsewhere in the body.
Trans-Thoracic Needle Aspiration (TTNA)
TTNA is an outpatient procedure performed in radiology under CT guidance. A radiologist locates the lung lesion with the help of a CT scan and inserts a long, thin needle through the skin and into the lung in an attempt to obtain a sample of the lesion. The sample is then sent to the pathologist for diagnosis. Patients are given numbing medicine before the procedure to make them more comfortable.
Surgical Open Lung Biopsy using VATS
Surgical open lung biopsy occurs in the operating room under general anesthesia. This is most commonly done with tiny, five mm incisions, using video-assisted thoracoscopy (VATS). On occasion, if the nodule is too deep within the lung, a tiny wire is placed the moring of surgery next to the nodule using CT-guidance. The nodule is then resected by VATS in the operating room, again, using the tiny five mm incisions.