How does measurement of the doubling time of nodules aid in the determination of a benign solitary pulmonary nodule?
Doubling time, the time required for a nodule to double in volume (equivalent to an increase of about 26% in diameter), for most malignant nodules is 1 to 15 months. Nodules that double in volume more rapidly or more slowly than this tend to be benign. Generally, lack of growth of a nodule over a 2-year period is strongly suggestive of benignancy, although some malignant nodules, such as nodules secondary to AIS, MIA, bronchial carcinoid, or some pulmonary metastases, may take longer to grow. Initial follow-up CT scans for indeterminate pulmonary nodules generally are performed 3 to 12 months after the initial CT scan to assess for interval growth depending on the size and appearance of the nodule and the presence of risk factors for malignancy, such as a patient history of tobacco use.
