From the Guidelines
No, these small nodules do not require follow-up based on current guidelines. The 0.4 cm non-calcified nodule in the left lower lobe and the 0.3 cm non-calcified nodule in the left upper lobe/apex are both less than 6 mm in size, which falls below the threshold requiring routine surveillance, as stated in the guidelines for management of incidental pulmonary nodules detected on CT images from the Fleischner Society 2017 1.
Key Points to Consider
- For lung nodules smaller than 6 mm, the risk of malignancy is extremely low, and the potential harms of additional imaging, including radiation exposure and unnecessary anxiety, outweigh the benefits.
- These tiny nodules are commonly found incidentally on CT scans and are typically benign findings that represent small areas of scarring, inflammation, or normal lymph nodes.
- However, if the patient has significant risk factors for lung cancer, or if there are concerning clinical symptoms, their physician might consider follow-up imaging despite the small size.
Guideline Recommendations
- According to the Fleischner Society 2017 guidelines, nodules less than 6 mm do not require routine follow-up in low-risk patients (recommendation 1A) 1.
- Certain patients at high risk with suspicious nodule morphology, upper lobe location, or both may warrant 12-month follow-up (recommendation 1A) 1.
Clinical Decision
- In the absence of significant risk factors or concerning clinical symptoms, no additional imaging is recommended for these nodules, as the benefits of surveillance do not outweigh the potential harms.
From the Research
Nodule Size and Follow-up
- The size of the nodules in question are 0.4 cm and 0.3 cm, which are both less than 1 cm and can be considered small non-calcified pulmonary nodules 2, 3.
- For nodules less than 10mm in size, management algorithms may vary depending on individual cancer risk, presence or absence of calcifications, and nodule size 3.
- A study recommends a follow-up CT at 12 months for nodules less than 4mm in high-risk persons, whilst for low-risk persons no follow-up is needed 3.
Growth and Malignancy Risk
- The risk of malignancy for small nodules is generally low, but can be increased by serial growth, diameter greater than or equal to 10 mm, and semisolid appearance 2.
- A study found that malignant nodules manifest growth slowly on follow-up CT, and 3-month follow-up CT has very low yield in showing nodule growth 4.
- The frequency of growth at 3 months was found to be 5% by linear and 7% by volumetric measurement, suggesting that stability at 3-month follow-up should not instill high confidence in benignancy 4.
Follow-up Recommendations
- For solid, smooth or attached indeterminate non-calcified nodules between 5 and 10mm, an annual repeat scan is recommended 3.
- For purely intra-parenchymal nodules, a 3-month repeat scan should be made to assess growth 3.
- A study found that none of the small noncalcified nodules grew and 14% decreased in size at follow-up CT scans performed within 12 months, suggesting that solid noncalcified subcentimeter nodules are nearly unchanged in size when a follow-up CT scan is done within 12 months 5.
Considerations for Follow-up
- The decision to follow up on small non-calcified pulmonary nodules should take into account individual cancer risk, nodule size, and other factors such as presence or absence of calcifications and nodule consistency 2, 3.
- The role of positron emission tomography (PET) in evaluating these nodules needs further exploration 2.
- Serial follow-up for 24 months in a high-risk cohort appears reasonable based on present data, but further longitudinal information is required 2.