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Probability of Malignancy in a Solitary Pulmonary Nodule Using the Equation of Swensen et al

Purpose: To estimate the probability that a solitary lung nodules is malignant using the equation of Swensen et al.

Description

Swensen et al used an equation based on clinical and radiologic findings to predict the probability that a solitary pulmonary nodule is malignant. This can help identify patients who may benefit from more aggressive diagnostic techniques or who may be able to be managed more conservatively.  The authors are from the Mayo Clinic.


Lesion size: from 4 to 30 mm

 

Exclusion: Patients with the diagnosis of cancer within 5 years prior to the identification of the nodule.

 

Parameters evaluated using multivariate logistic regression:

(1) age in years

(2) cigarettes

(3) cancer history

(4) diameter of lesion in mm

(5) spiculation

(6) lobe

 

Parameter

Finding

Points

cigarette smoker

current or former smoker

1

 

never a smoker

0

cancer history

history of an extrathoracic cancer diagnosed more than 5 years ago

1

 

no such history

0

spiculation

spicules along the edge of the nodule

1

 

no spicules

0

lobe

in upper lobe

1

 

not in upper lobe

0

 

where:

• After a period of time a former cigarette smoker's risk decreases, so there may need to be a time constraint on scoring cigarette smoking.

• Smoking cigars and pipes may confer some risk for lung cancer.

 

X =

= (0.0391 * (age in years)) + (0.7917 * (points for cigarettes)) + (1.3388 * (points for cancer history)) + (0.1274 * (diameter in mm)) + (1.0407 * (points for spiculation)) + (0.7838 * (points for lobe)) – 6.8272

 

probability of malignancy =

= EXP(X) / (1 + EXP(X))


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Specialty

Objective

ICD-10