CT screening can reduce lung cancer mortality

Patient in a CT machine Source: Johnny Greig via Getty Images

Structured lung cancer screening with low-dose computed tomography (CT) scans can reduce lung cancer mortality in both current and former smokers. This is the conclusion of the Federal Office for Radiation Protection (BfS) in a report published in the Federal Gazette on 6 December 2021.

The report forms the scientific basis for the approval of this early detection measure in the form of a legal ordinance by the Federal Ministry for the Environment, Nature Conservation and Nuclear Safety (BMU).

Paulini says that high quality requirements are necessary

"Our scientific report highlights the potential of lung cancer screening using low-dose CT. Accordingly, the mortality rate from lung cancer can be reduced in smokers. However, the benefit of such an early detection measure with X-rays for the individual and society can be achieved only if high quality requirements are met", says Inge Paulini, president of the BfS.

The specific implementation of early lung cancer detection with low-dose CT will be essential for this. In addition to defining the participation criteria, this also includes requirements and specifications regarding the CT equipment, the performance of the examination and the reporting, and the training of the medical personnel. Other points are quality assurance along the entire process and the thorough scientific evaluation of the results achieved.

"These aspects will also play a central role in the evaluation of other screening examinations that involve radiation protection", says Paulini.

Mammography screening the only approved procedure to date

To date, mammography screening for the early detection of breast cancer is the only approved procedure for X-ray screening in Germany. With the Radiation Protection Act, which came into force at the end of 2018, the BMU was authorised to issue further X-ray examinations for early detection by means of corresponding legal ordinances.

For each new examination procedure under consideration, the BfS prepares a scientific report in which the benefits and risks are weighed against each other. Minimum standards for carrying out the examination are also recommended. Until a legal regulation comes into force, lung cancer screening with low-dose CT scans is prohibited.

New screening for high-risk group

LDCT image of the lungs Source: Pijitra/Stock.adobe.com

Lung cancer still has an unfavourable prognosis because it is usually discovered only at a late stage. Both long-time smokers over 50 years of age and ex-smokers who have smoked for a long time are considered to be at risk. Imaging methods such as low-dose CT are generally considered for the early detection of lung cancer.

The risk-benefit assessment is particularly important because people without symptoms of disease are also examined. However, only a small proportion of these actually have the disease and can thus directly benefit from the examination. On the other hand, the risks – such as the radiation risk – are borne by all participants.

On behalf of the BMU, the BfS conducted a scientific assessment based on 38 publications on randomised controlled trials. The meta-analysis, which included data from 70,000 individuals, showed evidence of a benefit from screening heavy smokers.

In the group of participants examined with low-dose CT, lung cancer mortality was reduced by 15% compared with the control group. This means that for every 1,000 participants, three fewer people die of lung cancer over a period of about 10 years after the start of screening.

Possible overdiagnosis and false positive findings

The risks of early detection include overdiagnosis. This means the diagnosis of tumours that would never have been noticed without screening and would not have needed treatment. For lung cancer screening, the studies showed that the risk of overdiagnosis is not negligible; however, the exact number is difficult to quantify and varies between studies.

The CT scans also reveal abnormalities that lead to further examinations and interventions. However, the suspicion of a tumour is ultimately not confirmed. These false positive findings were found in up to 25% of low-dose CT scans in the studies after the fact.