A variety of inflammatory shadows caused by COVID-19 on chest CT that closely resembled lung cancer in annual lung cancer screening.
Authors: Kimura Tatsuo , Fukumoto Shinya , Nakano Akemi , Uchida Sawako , Nadatani Yuji , Motoyama Hiroyuki , Tauchi Yukie , Takashima Shingo , Kanamori Atsushi , Sawa Kenji , Ageshio Naomi , Watanabe Toshio 
Published: June 2024

e23122 Background: Chest X ray (CXR) has been the most common screen test procedure for detection of lung cancer. Before COVID-19, we have shown that repeat visitors (R) had a significantly lower proportion of CXR abnormalities requiring medication than the first-time visitors (F) at annual lung cancer screening. (Kimura T. Health Prim Car, 2021). During COVID-19, we reported that the influence of large waves of COVID-19 in annual lung cancer screening. (Kimura T. abstract No. e18596, ASCO annual meeting 2023) Because of the widespread use of vaccines, the XBB variants, derived from Omicron BA.2, has mainly cold-like symptoms. These variants spreads more easily than the original or the Delta variants. In Japan, since May 2023, COVID-19 has been made less dangerous under the Infectious Disease Control Law, which loosens the restrictions on wearing masks and having close contacts. No longer visits the hospital unless there is a high fever or dyspnea. Hypothesis is that there is a difference in lung cancer screening after a COVID-19 infestation compared to during and before COVID-19. Methods: Our clinic “MedCity21” is a university outpatient clinic for medical check-ups as a part of private health screening programs. Our facility allows COVID-19 diagnosed participants (pts) 5 days after onset or 24 hours after symptoms have abated. When the abnormalities were detected on CXR, pts were notified in a week by telephone request and invited to our specialty clinic for chest CT scan as further examination. By year from 2018 to 2023, we examined the varieties of abnormal shadows on CXR and CT and compared the differences using the chi-squared tests. Results: In 2023, there were 15072pts were visited our clinic for private health screening, among them, 13451pts (F:23.8%, R:75.2%) had chest X-rays performed. The January 2022, percentage of pts with a history of COVID was 1.68%, gradually increased, reaching 46.6% in December 2023. There were 226pts (1.68%) with CXR abnormalities requiring further investigation. The rates in F and R were 3.06% and 1.23%, respectively. The distributions of CXR and CT variations on R group were consistent with our previous report. However, significantly increased rate of inflammatory changes in CT findings (16.3%) in F group compared to each previous year (3.2-6.9%). (p = 0.014) We experienced a variety of inflammatory shadows on chest CT that closely resembled lung cancer. Such shadows were confirmed to have shrunk or disappeared on CT scan 1-2 months later. Conclusions: The pts who had ever had COVID-19 gradually increased. This was accompanied by an increase in the number of inflammatory shadows that were difficult to differentiate from lung cancer. It is better to follow up patients with CT or CXR for a month instead of immediately examining them. COVID-19 may cause concomitant bacterial or viral pneumonia; COVID-19 may affect the immune mechanisms of healthy individuals.