MA03.06 Descriptive Epidemiology of Significant Incidental Findings in a Large Clinical Lung Cancer Screening Program

The identification and reporting of significant incidental (non-lung cancer) findings in CT lung screening (CTLS) has not been standardized, though there is an available modifier in the LungRADS structured reporting system to identify a scan as including a significant incidental finding. In this study, we describe the significant incidental findings and follow-up in a large, established clinical CTLS program. We retrospectively reviewed all of the clinically significant or potentially significant non-lung cancer findings, which we will refer to as significant incidental findings, for patients undergoing clinical CTLS in our program from January 2012 through December 2016 with follow-up through December 2017. Significant incidental findings were defined as any unexpected new and/or unknown non-lung cancer finding requiring clinical or imaging evaluation prior to the next CTLS exam. Given the high prevalence of coronary artery calcifications and emphysema in the CTLS population, these findings were not classified as significant incidentals. We describe the site of the incidental finding, the follow-up intervention, and the outcome. We also calculate the cancer detection rate for non-lung cancers. Of the 6482 scans performed during the study window, 286 (4.4%) reported a significant incidental finding. These findings were reported in 276 (9.4%) of the 2927 patients screened during that time. Nine patients had more than one CTLS exam with a significant incidental finding. The majority of incidental findings were found in the kidneys (18%), liver (14%), and thyroid (11%). There were 15 non-lung cancers diagnosed for a cancer detection rate of 5.4%. The most common intervention, 43%, involved additional imaging, while 26% had a follow-up phone call or consult with a physician. Biopsy was performed in 9.1% and 6.7% had surgery. Surveillance was recommended for 43.4% of the findings, medical intervention was required for 12.3% of non-cancer findings and 12.9% of findings required no additional follow-up. There were 25 (8.7%) significant incidental findings with unknown follow up and outcomes and 31 (10.8%) that resulted in not finding anything on follow-up to explain the finding seen on the CTLS. Only 4.4% of all scans in our CTLS program reported a significant incidental finding. Almost 70% of the 286 significant incidental findings identified conditions requiring medical treatment, surgical intervention, or surveillance. There was one non-lung cancer diagnosis for every 7.5 lung cancers diagnosed in our screening program.