From the Guidelines
Incidental lung nodules less than 6 mm in size do not require routine follow-up, unless they have suspicious imaging features that increase the malignancy risk. For incidental indeterminate pulmonary nodules measuring less than 6 mm on chest CT, the Fleischner Society guidelines do not recommend routine follow-up given the likelihood of malignancy is less than 1% 1. However, there are exceptions for nodules with suspicious imaging features that increase the malignancy risk to the 1% to 5% range. Some key factors to consider in the follow-up of incidental lung nodules include:
- Nodule size: nodules less than 6 mm have a low risk of malignancy, while those 6-8 mm require follow-up CT at 6-12 months, and those larger than 8 mm warrant more aggressive evaluation 1
- Nodule characteristics: solid nodules require different management than ground-glass or part-solid nodules, with the latter needing longer surveillance 1
- Patient risk factors: smoking history, age over 40, family history of lung cancer, and underlying lung disease influence follow-up intensity 1 The follow-up schedule should continue until stability is demonstrated for at least 2 years for solid nodules and longer for ground-glass opacities. CT is the modality of choice for evaluating pulmonary nodules, and low-dose technique is recommended for follow-up CTs 1. IV contrast is not required to identify, characterize, or determine stability of pulmonary nodules in clinical practice 1.
From the Research
Incidental Lung Nodule Follow-Up
- Incidental lung nodules are identified in approximately 1.6 million patients per year in the US and are detected on approximately 30% of computed tomographic (CT) images of the chest 2.
- The probability of malignancy is less than 1% for all nodules smaller than 6 mm and 1% to 2% for nodules 6 mm to 8 mm 2.
- Nodules that are 6 mm to 8 mm can be followed with a repeat chest CT in 6 to 12 months, depending on the presence of patient risk factors and imaging characteristics associated with lung malignancy, clinical judgment about the probability of malignancy, and patient preferences 2.
Management of Incidental Lung Nodules
- The management of incidental lung nodules should reflect a balance of malignancy risk and the clinical context in which nodules are discovered 3.
- Nodule size, attenuation, morphology, and location all influence the likelihood of malignancy and, thus, the necessity and timing of follow-up according to current Fleischner recommendations 3.
- Established guidelines address the reporting and management of incidental pulmonary nodules, both solid and subsolid, synthesizing nodule and patient features to distinguish benign nodules from those of potential clinical consequence 4.
Follow-Up and Treatment
- The treatment of an individual with a solid pulmonary nodule 8 mm or larger is based on the estimated probability of malignancy; the presence of patient comorbidities, such as chronic obstructive pulmonary disease and coronary artery disease; and patient preferences 2.
- Management options include surveillance imaging, defined as monitoring for nodule growth with chest CT imaging, positron emission tomography-CT imaging, nonsurgical biopsy with bronchoscopy or transthoracic needle biopsy, and surgical resection 2.
- Part-solid pulmonary nodules are managed according to the size of the solid component, with larger solid components associated with a higher risk of malignancy 2.
- Ground-glass pulmonary nodules have a probability of malignancy of 10% to 50% when they persist beyond 3 months and are larger than 10 mm in diameter 2.
Recent Advances and Future Perspectives
- Recent advances in CT, PET/CT, MRI, radiomics, and deep learning technology have shown promising results in the characterization and prognostication of pulmonary nodules 5.
- Technical advancements in MRI and PET/CT provide functional information about malignant nodules, and advances in tissue biopsy techniques enable molecular analysis and histologic diagnosis of indeterminate nodules 5.
- New techniques such as radiomics, deep learning technology, and artificial intelligence are being investigated for their potential to differentiate between malignant and benign nodules 5.