Like many European countries, including France, lung cancer is the number one cause of cancer death in South Korea (1). As of 2020, the crude mortality rate of lung cancer in Korea was 36.4 per 100,000 people, accounting for 22.7% of all cancer deaths (2).
In 2015, the Korean multi-society collaborative committee announced a guideline for lung cancer screening, which recommended annual screening with low dose chest CT (LDCT) in high-risk subjects aged 55 to 74 years with a smoking history of 30 pack-years or more within 15 years (3). The guideline also stated that LDCTs should be obtained with multi-detector CT scanners with 16 rows or more and interpreted by radiologists.
After the announcement of the guideline, the Korean Lung Cancer Screening Project (K-LUCAS) was conducted between 2017 and 2018, before the formal implementation of the national lung cancer screening program (4). The K-LUCAS was a national project prepared by the Ministry of Health and Welfare, and many medical societies, including the Korean Society of Radiology and the Korean Association for Lung Cancer, collaborated on the project. A total of 13,692 participants underwent screening LDCTs in 14 participating institutions (national cancer center, ten regional cancer centers across the nation, and three university hospitals in Seoul). Among them, 90 were diagnosed with lung cancer, accounting for 0.66% of the participants. 90% (81) of lung cancers were non-small cell lung cancers, and 56 of them were adenocarcinomas. Regarding the stage distribution, 53.3% (48) were stage I lung cancers.
Based on the experience of K-LUCAS, the national lung cancer screening program was started in 2019 for current smokers first. For the recruitment of participants, screening invitations are initially sent to potentially eligible individuals (aged 54 to 74 years with a smoking history of 30 pack-years or more) based on the questionnaire completed in the prior national cancer screening. After confirmation of the eligibility, participants undergo screening LDCTs, followed by counseling for the result and a smoking cessation program (5).
A multi-detector CT scanner with 16 rows or more should be used to acquire CT images. Transverse CT images should be reconstructed with 1.0- or 1.25-mm slice thickness with a high-frequency kernel, and multi-planar reconstruction is recommended for better characterization of nodules. Regarding the radiation dose, the volume CT dose index should be 3.0 mGy or less for standard-sized subjects (5).
LDCTs should be interpreted by a board-certified radiologist who completed an educational program. A modified version of lung CT screening reporting and data system (Lung-RADS) has been used for the interpretation and reporting. Category 3 or 4 nodules with additional features suggesting benignancy can be downgraded to category 2b, indicating a negative screening result. In the K-LUCAS, the lung-RADS-based positive screening rate was 15.3%. A high prevalence of tuberculosis sequelae (13%) might be associated with a relatively high positive screening rate (6). Modifying the nodule size threshold to define positive screening results might be considered to reduce the false-positive rate. In the retrospective analysis of the K-LUCAS result, elevating the diameter from 6 to 9 mm for solid nodules led to only a modest reduction in sensitivity for lung cancer (96.2% to 94.2%), with a 60% reduction of unnecessary follow-up LDCTs (7).
Computer applications for LDCT interpretations, including computer-aided detection and measurement of lung nodules, have been expected to help reduce the variability of interpretations. In the K-LUCAS, a computerized interpretation system incorporating computer-aided detection and semi-automated measurement of lung nodules was established via a thin-client system (Figure 1). LDCT images were uploaded to a cloud computer, and radiologists could interpret LDCTs using the interpretation system without the installation of the system in individual screening institutions (8). After the implementation of the cloud-based computerized interpretation system in K-LUCAS, the variability of positive screening rates across institutions was significantly reduced (8). The accumulation of LDCT images and interpretation results in the cloud system may also help quality assurance of image acquisition and interpretation.
Apart from the solid evidence for the effectiveness of lung cancer screening with LDCTs, multidisciplinary efforts and cooperation are essential to solving various practical issues (e.g., recruitment of participants, education of professionals, quality control and monitoring, smoking cessation program) in the actual implementation of a nationwide lung cancer screening program. The experience of K-LUCAS suggested the feasibility of a nationwide lung cancer screening using a cloud-based computerized interpretation system (9). Refinement of the screening program with accumulated experience and data from the K-LUCAS and national lung cancer screening program might be also possible to maximize the benefit of lung cancer screening while minimizing unnecessary cost or harm.
Image
Figure 1. User interface of cloud-base computerized interpretation system
References
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Hwang EJ, Goo JM, Kim HY, Yi J, Kim Y. Optimum diameter threshold for lung nodules at baseline lung cancer screening with low-dose chest CT: exploration of results from the Korean Lung Cancer Screening Project. Eur Radiol. 2021;31(9):7202-12.
Hwang EJ, Goo JM, Kim HY, Yi J, Yoon SH, Kim Y. Implementation of the cloud-based computerized interpretation system in a nationwide lung cancer screening with low-dose CT: comparison with the conventional reading system. Eur Radiol. 2021;31(1):475-85.
Lee J, Kim Y, Kim HY, Goo JM, Lim J, Lee CT, et al. Feasibility of implementing a national lung cancer screening program: Interim results from the Korean Lung Cancer Screening Project (K-LUCAS). Transl Lung Cancer Res. 2021;10(2):723-36.
