Low-dose computed tomography (LDCT) screening for lung cancer is effective in reducing mortality from lung cancer in high-risk individuals. Asbestos exposure increases the risk of lung cancer and when combined with a tobacco exposure the risk is near multiplicative. To be eligible for LDCT screening in the USA, the US Preventative Services Task Force (USPSTF) require individuals to fit the following criteria: age 55-80, ≥30 pack-years of smoking, <15yrs since quitting. The National Comprehensive Cancer Network (NCCN) reduce the required pack years to >20 with concurrent occupational carcinogen exposure. We report the preliminary findings from LDCT screening of an asbestos-exposed cohort from the Western Australia Asbestos Review Program (ARP).
Between 2012-2017 annual screening LDCT chest scans were offered to the ARP cohort (all with ≥3 months of cumulative asbestos exposure, regardless of tobacco smoke exposure). In addition, health questionnaires (including smoking status) and lung function tests were performed. An indeterminate nodule was defined as a nodule >5mm and/or >50mm3. All LDCT scans with nodules and other potentially clinically significant findings are reviewed routinely by our ARP multidisciplinary team for decisions on clinical follow-up. The outcomes of nodules, asbestos-related pleural disease and other incidental findings were analysed.
1743 patients (262 (15.0%) female) with a median (IQR) age of 69.8 (63.0 to 75.7) years underwent 5702 screening scans. 595 (34.1%) were never smokers, 131 (7.5%) were current smokers. Median pack year history was 17.1 (7.2 to 33.8). 236 (13.5%) individuals fitted USPSTF criteria and 258 (14.8%) NCCN criteria.
610 (35%) had CT features of asbestosis and (62%) had pleural plaque on LDCT. Prevalent nodules were detected in 115 (6.6%) individuals, 32 (1.8%) developed incident nodules. Over the 5 years, 171 (9.8%) underwent an additional follow-up scan for an abnormality (usually 3 months interval), 23 required 2 or more interval scans. Median estimated radiation exposure per scan was 0.2 mSv.
Lung cancer was confirmed in 18 (1.0%) and 7 mesotheliomas were diagnosed in the cohort.
Of those with lung cancer, only 3 would have been eligible for screening under USPSTF guidelines or NCCN criteria. Significant incidental findings included lymphoma, metastatic melanoma and a slipped gastric band.
This asbestos-exposed cohort has a rate of lung cancer comparable to other high-risk smoking cohorts, despite modest tobacco exposure. Existing models of lung cancer risk estimate such as the USPSTF and NCCN criteria may not adequately account for the risk from asbestos exposure. Compared to other lung cancer screening cohorts we report a relatively low proportion of indeterminate pulmonary nodules, this may be due to lower tobacco exposure, the definition used for an indeterminate nodule and/or variance by geographic location.