used for screening lung cancer in high-risk
patients sometimes detect the presence of small lung
nodules. However, these
nodules may not always mean cancer, and have to be investigated further. A
recent study tried to establish factors that could be associated with the
probability of a nodule detected on low-dose CT scan to be cancerous.
The study was conducted in patients enrolled in the
multicenter Pan-Canadian Early Detection of Lung Cancer Study (PanCan) and in
chemoprevention trials conducted by the British Columbia Cancer Agency (BCCA). The
participants were between 50 and 75 years of age and were smokers
, either in
the present or in the past. Thus, these patients were at a higher risk for lung cancer
. The patients were given a questionnaire and a spirometry test to study
the lung function was performed.
Low-dose CT scans were performed on the patients and
the presence of nodules or other abnormalities suggestive of cancer were noted.
Patients with a noncalcified lung nodule were followed with repeat CT scan a
few months later till it could be established whether the nodules were benign
or malignant. The presence of lung cancer was confirmed based on the results of
biopsy of the nodule. The patients were followed up for a period of 2 years.
In the PanCan patients, around 5.5% of the total
number of patients with nodules detected on the screening turned out to be
suffering from cancer. In the BCCA study, 3.7% patients among the patients with
nodules had cancer
The study evaluated certain variations that could
make it more likely for the nodules detected on the CT scan to be malignant. These
included the size, type, number and location of the nodules, and the presence
of speculation (spike-like appearance).
The nodules in the upper lobes were more commonly
cancerous than the ones in the middle or lower lobes. Nodules that were located near lung fissures
were unlikely to be cancerous. Other factors that were more commonly associated
with cancer were older age of the patient, female sex, presence of family
history of lung cancer or emphysema
in the patient. In addition, cancerous
changes were also more commonly associated with larger nodules, nodules that
were part-solid, and the presence of spiculation of the nodule on the scan. Patients
with a lower nodule count also had higher chances of cancer.
The authors also caution that these results cannot
be applied to people at low risk of developing lung cancer
, or those with
nodules detected between the lungs or near the lungs roots; these nodules have
to be evaluated further.
Probability of Cancer in Pulmonary Nodules Detected on First Screening CT;
Annette McWilliams et al; N Engl J Med 2013; 369:910-919.