According to the American College of Radiology (ACR) appropriateness criteria, a nodule is any lung lesion that is a discrete, spherical opacity, 2-30 mm in diameter surrounded by normal lung tissue. Lesions greater than 30 mm are called masses and are evaluated differently than nodules. Multiple pulmonary nodules are evaluated the same as a solitary nodule, with the size of the largest nodule being used for the guideline. Criteria published by the ACR, American College of Chest Physicians, and the Fleischner Society are combined by major radiology benefits managers (RBM) to determine the best way to follow pulmonary nodules.
If a pulmonary nodule is discovered by chest x-ray or any non-chest imaging study (such as abdominal CT, a spine MRI, or a coronary CTA), RBM guidelines support performing one initial dedicated CT scan of the chest with contrast (71260). Contrast is usually preferred (in the absence of renal disease or dye allergy) because a non-contrast CT may miss abnormal lymph nodes or vascular features. The CT chest (with or without contrast) is then interpreted for
• any other characteristic such as ground-glass, calcification, spiculation or multiple nodules which may be a clue for metastatic disease.
High vs. Low risk patient factors
Historical and patient information, such as smoking history, past history of granulomatous diseases, family history of lung cancer and any other cancers, immunocompromised states, and exposure to any carcinogens, are helpful in assessing risk. Patients with solid nodules smaller than 6 mm and no patient factors are considered at low risk, and one radiology benefit management company’s guideline does not support any follow-up imaging. Comparison of a nodule to prior x-rays or scans for interval growth or change in characteristics also is helpful in determining follow up imaging.
If a low dose screening CT scan for lung cancer (usually done without contrast) demonstrates a nodule that can be measured and interpreted, repeating the scan is not necessary until the designated surveillance time-frame (below) for that size nodule.
Where do we go from here? CT Surveillance.
If a nodule is discovered and found to have none of the radiologic features of a malignancy (spiculation, abnormal calcification, sub-solid appearance, ground glass opacities) CT surveillance begins with the first assessment for size and stability and continues for a specified period of time (see table below). A solid nodule less than 6 mm should be evaluated with another CT scan in 12 months, and if unchanged, no follow-up is necessary. Ground glass and sub-solid nodules less than 6 mm may be followed-up with another repeat CT at 2 and 4 years from discovery.
Solid nodules 6-8 mm in size should be followed up with repeat CT at 6-12 months, a second scan at 18-24, and if no change at 24 months, no follow up is necessary. Sub-solid and ground glass nodules greater than 6 mm should be followed at 6-12 months and then annually for a total of 5 years.
A solid nodule greater than 8 mm may have repeat CT scans at 3-6 months and another at 18-24 months. Because of the size, PET scan or biopsy may also be considered and would be approved.
Is PET scan ever indicated in CT surveillance?
If a solid nodule greater than 8 mm is initially described, a single PET scan can be approved and performed. If the PET is positive, biopsy is recommended because false positive PETs may occur due to infection or inflammation. If the PET is negative, repeating PET is not indicated, rather, guidelines support follow-up CT scan in 6 months after the PET, and thereafter, additional CT scans for 24 months. If any of these scans show growth of the nodule at any time, biopsy is recommended.
Lung nodules that increase in size or number are no longer considered part of surveillance and should be evaluated with PET or biopsy. In any size nodule if there is a history of a malignancy that may metastasize to the lung, PET guidelines for suspected recurrence or re-staging for that cancer should be referenced. This applies whether the nodule is intra-pulmonary or pleural.
Stability and Continuing CT surveillance
Additional imaging with CT scans are not necessary if:
• A nodule was less than 6 mm and stable for 12 months
• A nodule greater than 6 mm with no worrisome features and is stable over 24 months
• If a past chest x-ray demonstrates stability of a nodule over 2 years
• Nodules are decreasing in size or disappearing
• Radiographic interpretation describes benign features such as calcification pattern typical of a granuloma or a hamartoma.
Lesson #31 The discovery of pulmonary nodule(s) on a chest x-ray or non-pulmonary imaging study is a finding that must be followed-up using criteria from established guidelines. Radiology benefits management companies often combine the recommendations from several pulmonary, radiology, and oncology organizations to form a concise and easy to follow protocol. Refer to these guidelines to help you obtain authorization “right out of the gate” without delays, denials, and peer-to-peer calls.
At a future post I will detail the guidelines for lung cancer screening.