P2.11-08 CT Screening of Never Smokers

Abstract

We wanted to update our previous reports of the impact of SHTS on lung cancer and cardiovascular disease in never smokers and the usefulness of low-dose CT (LDCT) screening using the I-ELCAP protocol. Never smokers, defined as having smoked less than 100 cigarettes in their lifetime, were enrolled in our LDCT screening program. All signed IRB-HIPAA compliant consents. Patient demographics, medical history, and validated SHTS-exposure questionnaire were obtained at baseline. The SHTS-exposure score was computed for all participants together with LDCT Ordinal score for coronary artery calcifications (CAC), emphysema, lung cancer diagnosis and treatment were documented. At two of the institutions, we also performed pulmonary function tests, and measured the main pulmonary artery (MPA) and ascending aorta (AA) measurements, determined the automated aortic calcium score and extent of atherosclerotic plaque present in the coronary arteries using CT angiograms. Frequency of abnormal pulmonary function (FEV1/FVC ratio<0.7) and MPA/AA ratio≥1.0 were evaluated. We examined the relationship between SHTS exposure and these disease conditions. Among 14,018 never smokers, 6733 (48.1%) were women, 7276 (51.9%) men. Among them, 5236 (37.4%) had at least one noncalcified nodules (NCNs). Of the 14,018, 855 (6.1%) had at least one NCN 6.0 mm but less than 15.0 mm for which follow-up LDCT is recommended and 113 (0.8%) had NCN 15.0 mm or larger (Table 1). Lung cancer was diagnosed in 55 (0.4%); 53(96.4%) resulting from findings on baseline LDCT and 2(3.6%) from the subsequent annual repeat LDCTs. Of the 55, 47 (85.5%) were clinical stage I; 49 had surgical resection, 4 treated with radiation therapy, and 2 with chemotherapy. Diagnosis was adenocarcinoma in 44, squamous-cell in 7, small-cell in 1 and other in 3. Post-surgically, 45 (81.8%) of the 47 were pathologic Stage IA (T1a-1cN0M0). Of the 14,018 never smokers, the CAC score was 0 for 10,956 (78.2%), 1-3 for 1941 (13.9%), and 4-12 for 1211(8.0%). Emphysema was present in 310 (2.2%) participants. The prevalence of lung cancer (p=0.04) was significantly associated with SHTS exposure, as was CAC (p<0.0001) and emphysema (p=0.03). In the subset of participants where additional measurements are available, abnormal pulmonary function tests (p=0.04), automated aortic calcium score (p=0.009), MPA/AA ratio≥1.0 (p=0.009) and presence and extent of coronary artery plaque (p<0.0001). These results suggest that LDCT screening is of benefit for never smokers exposed to SHTS for identification of early lung cancer, cardiovascular disease and emphysema.