What is the best course of action for a patient with a lung nodule that has increased in size from 0.7 cm to 0.9 cm, considering their smoking history and potential risk factors for lung cancer?

Management of Growing Lung Nodule (0.7 cm → 0.9 cm)

This nodule requires immediate tissue diagnosis through either PET-CT imaging followed by biopsy or direct surgical resection, as documented growth in a solid nodule strongly suggests malignancy and warrants definitive action rather than continued surveillance. 1

Why Growth Changes Everything

The critical issue here is documented growth from 7 mm to 9 mm, which represents approximately a 26% increase in diameter—this corresponds to a doubling in tumor volume. 1 Growth detection in a solid nodule is one of the strongest predictors of malignancy, fundamentally changing the management approach from surveillance to active intervention. 1

• Malignant solid nodules typically double in volume within 400 days, and your patient's nodule has demonstrated clear growth. 1
• Approximately 20% of malignant nodules may temporarily decrease in size, but sustained growth is highly suspicious. 1
• The surveillance strategy's primary risk is that malignant tumors can progress from resectable to unresectable disease during observation, missing the window for surgical cure. 1

Risk Stratification Using Clinical Predictors

Now that growth is documented, you must calculate the pretest probability of malignancy using validated models. 1

Key risk factors to assess:

• Age: Each additional year increases odds by 1.04 (OR 1.04 per year). 1
• Smoking history: Current or former smokers have OR 2.2 for malignancy. 1
• Nodule characteristics: Spiculation (OR 2.8), upper lobe location (OR 2.2). 1
• Prior cancer history: Extrathoracic cancer >5 years ago (OR 3.8). 1
• Current size: At 9 mm diameter, each millimeter adds OR 1.14. 1

The Mayo Clinic model is the most extensively validated and should be your primary tool, particularly as it has demonstrated superior accuracy (AUC 0.747) compared to the Brock model (AUC 0.713) in large population-based studies of incidental nodules >8 mm. 2

Management Algorithm for Growing Nodules ≥8 mm

Step 1: Calculate Malignancy Probability

Use the Mayo Clinic formula with the patient's specific characteristics. 1 The British Thoracic Society guidelines note that the Brock model may underestimate risk in growing nodules, making Mayo preferable in this context. 1

Step 2: Determine Next Action Based on Probability

If probability is LOW (<5%):

• This scenario is unlikely given documented growth, but if present, consider short-interval CT surveillance at 3 months to confirm continued growth pattern. 1
• However, any documented growth should raise suspicion regardless of calculated probability. 1

If probability is INTERMEDIATE (5-65%):

• Proceed with FDG-PET/CT imaging as the next diagnostic step. 1, 3
• PET-CT increases diagnostic accuracy substantially, with AUC improving from 0.79 to 0.92 when PET findings are incorporated. 1, 3
• After PET-CT, recalculate risk using the Herder model, which incorporates PET findings and demonstrates the highest accuracy in validation studies. 1, 3
• Important caveat: PET-CT sensitivity may be reduced in nodules <10 mm, but at 9 mm with documented growth, it remains valuable. 3

If probability is HIGH (>65%):

• Proceed directly to surgical resection in operative candidates, treating as presumptive localized lung cancer. 3
• For patients at high surgical risk, consider nonsurgical biopsy (bronchoscopy or transthoracic needle aspiration) with sensitivity of 70-90% for lung cancer diagnosis. 4

Step 3: Tissue Diagnosis

Given documented growth, tissue diagnosis is essential regardless of imaging findings. 1

• Bronchoscopy or transthoracic needle biopsy: Current methods yield 70-90% sensitivity for lung cancer diagnosis. 4
• Surgical resection: Provides both diagnosis and definitive treatment for operative candidates with high probability lesions. 3

Critical Pitfalls to Avoid

Do not continue surveillance alone once growth is documented—this is the primary error that leads to progression from resectable to unresectable disease. 1 The traditional "2-year stability rule" applies to nodules WITHOUT documented growth; your patient has failed this criterion. 1, 5

Do not rely solely on calculated probability models when growth is present—growth itself is a powerful independent predictor that may override lower calculated probabilities. 1

Do not delay action based on smoking status—while never-smokers have lower baseline risk (5.4% vs 17.7% in current smokers), cancer still occurs in 5.4% of never-smokers with nodules >8 mm, and growth makes this patient higher risk regardless. 2

Smoking History Considerations

If the patient is a current or former smoker, the probability of malignancy is substantially higher (12.2% for former smokers, 17.7% for current smokers with nodules >8 mm). 2 Combined with documented growth, this mandates aggressive evaluation.

If the patient is a never-smoker, the baseline probability is lower (5.4%), but documented growth remains highly concerning and requires the same diagnostic workup. 2 The Mayo model accounts for smoking status in its calculation. 1

Practical Next Steps

1. Obtain detailed smoking history (pack-years, current vs former, years since quitting). 1
2. Review nodule characteristics on CT: spiculation, margins, upper vs lower lobe location. 1
3. Calculate Mayo Clinic probability using the validated formula. 1
4. Order PET-CT if probability is intermediate (most likely scenario with documented growth). 1, 3
5. Refer to thoracic surgery if probability is high or if PET-CT shows high uptake. 3
6. Ensure thin-section CT technique (≤1.5 mm) for all follow-up imaging to accurately assess growth. 3