Early Diagnosis of Lung Cancer: The Convergence of Imaging and Information Technologies

Abstract

Three of four patients newly diagnosed with lung cancer have metastatic disease not curable with current therapies. The small percent of patients diagnosed with disease limited to the lung are discovered when the cancer lesion is small and asymptomatic. In the modern era of high resolution computed tomography (CT) scanning, early cancers may be seen as “indeterminate lung nodules”—noncalcified, rounded opacities ranging from 2 to 30 mm in diameter. 1 Small lung nodules, defined as 4 to 8 mm diameter, have variable risk for malignancy but are usually too small and inaccessible for successful biopsy. 2 Serial imaging is recommended by the Fleischner Society to ascertain whether growth rates are characteristic for malignancy. 3 However, scientifically based evidence supporting specific approaches to management of lung nodules found incidentally on chest CT is sparse. Most recommendations have come out of lung cancer screening trials, where asymptomatic volunteers agree to adhere to an a priori schedule of serial CT scans. The National Lung Screening Trial identified indeterminate lung nodules by CT among asymptomatic individuals with risk factors for lung cancer. 4 The trial, which provided follow-up imaging combined with community-based diagnostic testing and treatment, resulted in reduced lung cancer death rates among participants screened with chest CT compared with those screened with chest radiograph. This result is good news for the millions of smokers and prior smokers at risk of lung cancer, because it seems that chest CT may be an effective test for early diagnosis. The bad news for the medical care system is that approximately 25% to 50% of screenees have at least one indeterminate lung nodule greater than 4 mm diameter at baseline screening. 4–7 Although the great majority of such nodules will not prove to be malignant, follow-up imaging and testing will be needed to distinguish benign from malignant nodules. Thus, we are now fishing for a greater number of early-stage lung cancers in a sea of indeterminate small lung nodules. As the technology of imaging advances, knowledge of optimal management of lung nodules, and systems to support timely follow-up, must also advance.