Table 4.

Comparative presentation of currently published guidelines for the management of patients with lung nodules according to size and attenuation

Guidelines (references)	Nodule(s) size* and attenuation characteristics
	Small (diameter/volume)	Intermediate solid (diameter/volume)	Larger solid (diameter/volume)	Larger subsolid (diameter/volume)
Fleischner Society[1]	<6 mm/<100 mm3	6-8 mm/100-250 mm3	>8 mm/250 mm3	>6 mm/100 mm3
	Discharge or optional CT at 12 months depending on risk assessment (subsolid nodules necessitate more extensive follow-up at 2 years and 4 years)	Solitary nodules CT at 6-12 months and then at 18-24 months	Solitary nodules CT at 3 months or PET/CT scan, nonsurgical biopsy or surgical excision	Solitary pure ground-glass nodules  CT at 6-12 months and then every 2 years for a total of 5 years Solitary part-solid nodules  CT at 3-6 months and then annually for a total of 5 years, if solid component is stable and <6 mm. If solid component is≥6 mm or growing, proceed to PET/CT scan, nonsurgical biopsy, or surgical excision
	Multiple subsolid nodules  CT at 3-6 months and then optionally at 2 years and 4 years	Multiple nodules  CT at 3-6 months and then at 18-24 months (optional for low risk)	Multiple nodules  CT at 3-6 months and then at 18-24 months (optional for low risk)	Multiple nodules  CT at 3-6 months. Further management based on the most suspicious nodule(s)
BTS[2]	<5 mm/80 mm3	5-6 mm  CT at 12 months and if stable on volumetry†, discharge. If stable on diameter, repeat at 24 months	≥8 mm/≥300 mm3	≥5 mm
	Discharge	≥6 mm/≥80 mm3 CT at 3 months and if stable or VDT >400 days, repeat at 12 months and then as above	CT surveillance, nonsurgical biopsy, or surgical excision depending on serial risk assessments based on prediction models	CT at 3 months and then further CT surveillance (1, 2, and 4 years) or nonsurgical biopsy or surgical excision depending on risk assessment§
ACCP[3]	<5 mm CT at 12 months (optional for low clinical risk patients)	5-6 mm  Low clinical risk‡   CT at 12 months  High clinical risk‡   CT at 6-12 months and then at 18-24 months 7-8 mm  Low clinical risk‡   CT at 12 months and then at 18-24 months  High clinical risk‡   CT at 3-6 months and then at 9-12 months and 24 months	≥8 mm CT surveillance, nonsurgical biopsy, or surgical excision depending on clinical risk (PET/CT should precede further decisions in low-moderate risk patients) In patients with high surgical risk, CT surveillance or nonsurgical biopsy can be chosen depending on clinical risk and SBRT or RFA are recommended as alternatives to surgery	>5 mm Pure ground-glass nodules  Annual CT surveillance for at least 3 years (for nodules>10 mm early CT at 3 months followed by nonsurgical biopsy or resection are opted) Part-solid nodules  ≤8 mm   CTs at 3, 12, and 24 months and then annually for another 1-3 years  >8 mm  CT at 3 months followed by PET/CT scan, nonsurgical biopsy or surgical excision if persistent (for nodules>15 mm initial follow-up CT should be omitted)

*According to the Fleischner society guidelines, nodule diameter should be calculated as the average of long and short axes rounded to the nearest millimeter. ACCP and BTS guidelines define the reported diameter of a nodule as the maximum one, ^†BTS guidelines define significant nodule growth as a ≥25% volume change and discern evaluation strategies for growing nodules on the basis of the observed growth rate, as measured by VDT. CT surveillance continuation is proposed for nodules with a VDT >600 days, while a more aggressive workup with PET/CT, biopsy, or surgical excision is deemed necessary for rapidly growing nodules with a VDT≤400 days. Biopsy or ongoing follow-up with CT is recommended for patients with intermediate VDT (400-600 days) after taking into account patient perspectives, ^‡ACCP has introduced a trichotomous qualitative risk assessment model that assigns a high probability of malignancy (>65%) in older heavy smoking individuals with prior cancer and/or larger, spiculated nodules located in the upper lobes. The absence of these characteristics defines low probability of malignancy (<5%), while patients with a mixture of high- and low-risk features are considered to have an intermediate probability (5%-65%), ^§BTS guidelines are the only to emphasize the use of prediction models for nodule risk assessment. Based on the reported performance of different models, BTS recommends the application of Brock model for an initial algorithmic evaluation of patients with solid nodules >8 mm (or>300 mm³) followed by a second risk assessment using the Herder model in those with a Brock model score >10%. PET/CT scan is included in the Herder model and is, thus, a prerequisite for further evaluation of this group of patients. Follow-up is recommended for those with <10% malignancy risk based either on the Brock or the Herder model, while those with a higher Herder model risk score are candidates for nonsurgical biopsy (10%-70% risk) or surgical excision (>70% risk). Brock model, together with nodule morphology, is also recommended for risk assessment of subsolid nodules ≥5 mm. Of note, Brock model is the only prediction model suitable for multiple nodule risk assessment, as individuals with multiple nodules were included in its derivation cohorts. CT=Computed tomography, PET=Positron emission tomography, ACCP=American College of Chest Physicians, BTS=British Thoracic Society, VDT=Volume-doubling time