A solitary pulmonary nodule (SPN) detected on chest X-ray should be considered a potential alert to high-risk of developing lung cancer within five years, even in patients who are lifelong non-smokers, according to a study published online September 11, 2019 in PLoS One.
The study by Spanish researchers of 893 patients with a SPN revealed that the relative risk of lung cancer diagnosis was higher in women than men, and that factors associated with malignancy, such as COPD and a smoking history, were not significantly associated with lung cancer diagnosis or death.
The clinical population-based study looked at more than 25,000 patients who had a chest radiograph or chest computed tomography (CT) scan at the Peset Hospital in Valencia and San Juan Hospital in San Juan de Alicante during a two-year period starting in 2010. Ninety-one percent had a chest X-ray as their first imaging examination. None of the CT scans were performed for lung cancer screening. Over the next five years, 15% of patients with an SPN and 2% without developed lung cancer.
The authors sought to determine the factors associated with lung cancer diagnosis and mortality after an SPN is detected in routine clinical practice. Eight radiologists reviewed the 893 imaging cases in which an SPN between 3 and 30 mm had been detected. The radiologists recorded nodule size, shape, location, and nodule consistency for the 741 patients who underwent CT. The researchers also recorded smoking history, presence of chronic obstructive pulmonary disease (COPD), and prior malignancies for each patient.
Their analysis showed that women with an SPN had a lung cancer rate of 17.67 per 1,000 person-years, compared to 1.38 without an SPN; for men, the lung cancer rate was 32.35 and 6.22 per 1,000 person-years respectively. The researchers found that lung cancer patients without an SPN had a lower mortality rate, while smoking history affected mortality in men but was not significantly associated with mortality among women.
Lung cancer risk, as expected, was higher in patients with an SPN and a history of smoking, COPD, and were older. Twice as many male smokers with an SPN were diagnosed with lung cancer than women (21% compared to 10%), but the percentage of women nonsmokers who developed lung cancer was dramatically higher than male nonsmokers: 13% compared to 2%. Also, while COPD and a smoking history were associated with significant lung cancer risk in men with an SPN, the same was not true for women.
Among patients whose SPN was detected on chest CT, cancer risk was higher in both men and women, but twice as many female nonsmokers than male developed lung cancer: 12% versus 6%.
With respect to imaging characteristics, as nodule size increased on chest X-ray, lung cancer risk also increased: 19% for nodules between 12 mm and 28 mm, and 46% for nodules over 28 mm. Sixty percent of women and 45% of men with an SPN that had a spiculated border developed lung cancer. Men with a nodule in the upper lobes had a higher lung cancer risk, but this was not true for women.
On CT, the median SPN diameter of patients who developed lung cancer was 17 mm compared to 9 mm among those who did not. Men who developed lung cancer had much larger median SPN diameters than women: 19 mm versus 13 mm. Forty-eight percent of all patients with an SPN with a speculated border also developed lung cancer.
“With these findings, all guidelines for SPN management should include factors associated with malignancy for men and women separately. Or, the sex of a patient needs to be included as a lung cancer predictor in models,” wrote the authors.
Solitary pulmonary nodules in chest X-ray and CT: Risk factors in a clinical population. Appl Radiol.