Table 1

Key differences between the Fleischner Society 2017 and the British Thoracic Society 2015 recommendations for pulmonary nodules

Fleischner 2017British Thoracic Society guideline 2015
ScopePrimarily radiological management.Comprehensive management, from imaging to intervention.
ApplicabilityIncidentally detected pulmonary nodules.All pulmonary nodules regardless of presentation route.
Target populationAge 35 or older.Age 18 or older.
Solid nodules
 Recommended sizing method*Average short-axis and long-axis diameter (in the orthogonal plane which gives the largest two measurements).
Diameter rounded to the nearest whole millimetre.
(Volumetry parameters are also specified.)
Maximum diameter if volumetry unreliable/ unavailable.
 Size threshold for follow-up6 mm (NB: 5.5 mm or greater would be rounded up to 6 mm).
Caveat: Certain patients at high risk with suspicious nodule morphology, upper lobe location or both may warrant 12-month follow-up.
80 mm3 or 5 mm.
Caveat: Nodules smaller than this threshold which are definitely new compared with CT performed within the last 1–2 years merit follow-up.
 Definition of significant growth*≥2 mm diameter.>25% increase in volume (NB: use diameter measurements where volumetry is not possible or where there is clear evidence of marked growth).
 Follow-up intervalsRange of intervals rather than specified interval.
Medium (6–8 mm, 100–250 mm3) nodules:
Solitary: CT at 6–12 months, then CT at 18–24 months (consider need for longer follow-up if high risk).
Multiple: CT at 3–6 months, then consider CT at 18–24 months; use largest nodule to guide management.
Larger (>8 mm, >250 mm3) nodules: consider CT at 3 months, PET/CT or tissue sampling.
Prespecified intervals (3, 12 and 24 months).
Medium (5-8 mm, 80–300 mm3) nodules:
CT at 3 months; further follow-up based on VDT.
If diameter used, 5–6 mm nodules to be followed at 12 months.
No separate recommendation for multiple nodules; Brock model incorporates nodule count.
Use largest nodule to guide management.
Larger (>8 mm, >300 mm3) nodules:
Perform risk estimation with Brock model: risk ≥10% merits PET-CT; subsequent follow-up dictated by Herder model risk assessment.
(Herder score: <10% CT surveillance; 10%–70%—consider image-guided biopsy, excision or surveillance; >70% consider definitive treatment.)
 Follow-up duration (assuming interscan stability)Well-defined solid nodules with benign morphology at 12–18 months can be discontinued if the nodule is ‘accurately measurable and unequivocally stable’.If volumetry reliably used:
If volume stable (<25% change), discharge at 12 months; if VDT >600 days, consider discharge but option for CT surveillance.
If diameter used:
24 month follow-up.
Subsolid nodules
 Size threshold for follow-upSingle: 6 mm (NB: 5.5 mm or greater would be rounded up to 6 mm).
Caveat: In certain suspicious nodules <6 mm, consider follow-up at 2 and 4 years (eg, risk factors such as Asian populations). If solid component(s) or growth develops, consider resection.
Multiple: no lower threshold.
5 mm.
Caveat: no follow-up even if ≥5 mm if patient unfit for any treatment or stability from previous CT over 4 years.
No separate recommendation for single or multiple nodules.
 Follow-up intervalsSmall (<6 mm) single and multiple:
CT at 3–6 months.
If stable, consider CT at 2 and 4 years. Common recommendation for both pure ground-glass and part-solid nodules.
Larger (≥6 mm, ≥100 mm3)
  • Single ground-glass: CT at 6–12 months to confirm persistence, then CT every 2 years.

  • Single part-solid: CT at 3–6 months to confirm persistence. If unchanged and solid component remains, 6 mm, perform annual CT.

  • Multiple (ground-glass or part-solid): CT at 3–6 months. Subsequent management based on the most suspicious nodule(s).

  • Consider resection for growing nodules or those that develop a solid component.

Small (<5 mm): no follow-up.
Larger (≥5 mm): repeat CT in 3 months.
  • Stable: assess risk of malignancy with Brock model and morphology, patient fitness and patient preference.

    Caveat: Brock model may underestimate malignancy risk in persistent subsolid nodules.

    • Low risk (approximate Brock estimate <10%): CT at 1, 2 and 4 years from baseline.

    • High risk (approximate Brock estimate >10%) or concerning morphology, for example, solid component presence or growth, pleural indentation, vacuolation: discuss options for CT surveillance, image-guided biopsy, resection or non-surgical treatment.

  • Growth: resection, non-surgical treatment or observation (see main text for discussion).

  • Altered morphology (increasing density/new solid component): favour resection/non-surgical treatment.

 Follow-up duration (assuming interscan stability)Same recommendation for pure ground-glass and part-solid nodules.
Single: 5 years.
Multiple: dictated by the largest nodule.
4 years
Risk assessment*Applied to all nodule sizes.
Modified ACCP guidance.
  • Low risk: <5%.

  • High risk: ≥5%.

Assignment of risk primarily based on known risk factors (age, smoking history, family history, nodule morphology, spiculation, upper lobe location, emphysema, pulmonary fibrosis).
No specific model-based quantification suggested.
For solid nodules, risk assessment only suggested for large (>8 mm, >300 mm3) nodules.
Brock model.
  • Low risk: <10%.

  • High risk: ≥10%.

Herder model following PET-CT.
  • Low risk: <10%.

  • Intermediate risk: ≥10%–70%.

  • High risk: >70%.

  • *Denotes parameters where the guidelines differ, which are potentially most likely to create the greatest divergence in management recommendations. It should be noted that this is solely the view of the authors, in the absence of evidence comparing the two guidelines.

  • ACCP, American College of Chest Physicians; PET, positron emission tomography; VDT, volume doubling time.