New Fudan study: The impact of low-dose CT screening on the diagnosis of lung cancer in women

With the advancement of medical technology, cancer screening has become an important means of early detection and early treatment. Low-dose computed tomography (CT) screening for lung cancer has gradually become popular at home and abroad, and is considered an effective way to reduce the mortality rate of lung cancer. However, the problems of "overdiagnosis" and "overtreatment" caused by screening are also becoming increasingly prominent. To this end, the team of Professor Xu Wanghong from the School of Public Health of Fudan University, in collaboration with Professor Chen Haiquan from the Affiliated Cancer Hospital of Fudan University, and Zhang Li from the Shanghai Pudong New Area Center for Disease Control and Prevention, conducted a study on the overdiagnosis of lung cancer in women in my country, aiming to analyze the impact of low-dose CT screening on the diagnosis of lung cancer in women and provide a scientific basis for optimizing screening strategies.

Research process and findings

This study used Shanghai Pudong New Area as the research area and analyzed in detail the tumor registration report data from 2002 to 2020. After rigorous screening and collation, the information of approximately 3.21 million permanent residents was finally included to construct a large and detailed data set. During this period, a total of 46,978 new cases of lung cancer and 34,475 deaths were recorded, providing a rich sample for the study.

The researchers used the introduction of low-dose CT screening in 2011 as a key time point and divided the data into two periods, before and after screening, for comparative analysis. They carefully compared the age-specific incidence curves of lung cancer in the two stages, aiming to reveal the impact of screening on lung cancer incidence through this comparison, and further estimate the number and proportion of overdiagnosis.

To ensure the accuracy and scientificity of the study, the team used two key pieces of information to define the concept of "overdiagnosis." If the incidence of cancer increases significantly, while the mortality rate remains stable or decreases, and this phenomenon cannot be explained solely by the benefits of screening, it is considered a manifestation of overdiagnosis; if the incidence of early cancer increases, but the incidence of late-stage cancer does not decrease accordingly, this also implies that early tumors found in screening may not significantly affect the patient's life expectancy, thus constituting overdiagnosis.

The study found that the age-standardized incidence of lung cancer in women increased significantly between 2002-2005 and 2016-2020, from approximately 19.20 people diagnosed with lung cancer per 100,000 people to approximately 47.69 people diagnosed with lung cancer per 100,000 people, with an average annual growth rate of 3.11%. However, the mortality rate of lung cancer showed a downward trend during the same period, suggesting that there may be overdiagnosis.

Further analysis found that the incidence of stage I lung cancer in women increased significantly, but the incidence of advanced stage lung cancer did not decrease significantly, resulting in an overdiagnosis rate that surged from 22% from 2011 to 2015 to 50% from 2016 to 2020. In contrast, the incidence and mortality of lung cancer in men changed relatively steadily, and the overdiagnosis rate was even negative.

The study also pointed out that lung adenocarcinoma is the main type of overdiagnosis, with up to 88% of lung adenocarcinomas being overdiagnosed in female patients, compared to only 17% in male patients. The researchers speculated that this difference may be related to gender-specific risk factors and diagnostic behaviors.

Researchers believe that although lung cancer risk factors have improved in recent years, the surge in female lung cancer cases cannot be explained by these changes alone. Overdiagnosis is likely to be the main reason, and this problem needs to be paid attention to and solved in order to optimize the allocation of medical resources and reduce the burden on patients.

Future Outlook

This study revealed the problem of overdiagnosis of lung cancer in women caused by low-dose CT screening, posing a challenge to the formulation of screening strategies. The research team suggested adjusting the guidelines to reduce the frequency of screening for women in truly high-risk groups; at the same time, optimizing the management of lung nodules, combining the nature of the nodules and the patient's life expectancy to decide whether to perform surgery and when to do it, and reducing the impact of overtreatment; strengthening health science popularization, raising public awareness of the pros and cons of screening, and avoiding blindly following trends. Not only that, large-scale studies are still needed in the future to clarify the effects and risks of screening and provide a scientific basis for precise strategies. In general, while low-dose CT screening for lung cancer brings the benefits of early detection, it also brings the risk of overdiagnosis. It is hoped that in the future, under the guidance of scientific research and policies, everyone can find a balance so that cancer screening can truly play its due role and benefit the general public.

References: Xie D, Zhang L, He N, et al. Overdiagnosis of Lung Cancer due to Introduction of Low-Dose Computed Tomography in Average-Risk Populations inChina[J]. Journal of Thoracic Oncology, 2025.