CT Screening Effective in Reducing Lung Cancer Mortality Risk

Review examines two decades of research on CT screening in lung cancer in a controlled clinical setting


Even as smoking rates continue to decrease, lung cancer remains the most common cause of cancer death in the U.S., causing an estimated 143,000 deaths in 2019. With 228,000 new cases reported last year, it is also the second most frequent cause of cancer overall, behind prostate cancer for men and breast cancer for women.

Many lung cancers are diagnosed at a late stage and, therefore, are difficult to cure. However, accumulated evidence since the mid- to late-90s indicates that low-dose CT screening of high-risk patients enables the detection of lung cancer at an early stage. As a result, it can play a big role in reducing the mortality risk from lung cancer.

“Numerous studies demonstrate that low-dose CT screening for lung cancer can find more asymptomatic lung cancers than is possible by any other means,” said David S. Gierada, MD, a professor of radiology at the Washington University School of Medicine.

Dr. Gierada, who has been researching lung cancer screening for nearly 20 years, is the lead author of a recent Radiology: Imaging Cancer review article on the subject. The article provides a firsthand perspective on how lung cancer screening has advanced to its current state and where it is headed in the future.

“Although our intent was to be fully comprehensive, we also wanted to focus on how data and observations from these previous studies have led to the adoption of lung cancer screening in clinical practice and how these screenings are being conducted today,” Dr. Gierada said.

"As a result of these studies, CT screening is now a common part of radiology practice. But it must be implemented in a responsible way that follows the guidelines to make sure it is done as safely and effectively as possible."


Adoption of CT Screening is on the Rise

One of the key takeaways from the review is that the majority of lung cancers found by CT are detected at an early stage. Clinical trials have demonstrated that treatment of these screen-detected early-stage lung cancers can reduce the number of lung cancer deaths. Yet despite this potential, the adoption of CT screening has been relatively slow.

“These screenings were just approved for insurance coverage in 2015, so it took awhile for the practice to ramp up,” Dr. Gierada said.

But the number of lung cancer screening CT scans is beginning to grow. For example, a 2016 article referenced in the review noted that only 2% of eligible people underwent lung cancer screening, whereas that had increased to 14% in 2017.

Dr. Gierada stresses the importance of knowing the guidelines, eligibility requirements, protocols for managing findings, and risks as more radiology practices begin to implement lung cancer screening.

“Ordering a lung cancer screening test is more complicated than other diagnostic tests because there are specific age and smoking eligibility criteria,” he said. “This requires some calculations, and, for insurance coverage, certain documentation – and providers need to be aware of all these details.”

One of the most commonly cited risks of CT screenings for lung cancer is the potential for non-cancerous incidental findings. Although additional imaging does increase a patient’s risk to radiation exposure and additional diagnostic testing, Dr. Gierada notes that these risks are small and are very manageable so long as screening is done in compliance with recommended guidelines.

“This risk is now managed in a standardized way based on data from numerous studies and by using a CT assessment scheme that has guidelines for managing nodules based on size and density,” Dr. Gierada said. “The goal is to try to minimize the number of follow-up exams and the number of interventional procedures that are done for lesions that have a low likelihood of being cancer.”

Becoming Routine in Clinical Practice

The results of two decades of rigorous study have increasingly demonstrated that appropriate implementation of CT screening can prevent a substantial number of lung cancer deaths at low clinical risk.

“As a result of these studies, CT screening is now a common part of radiology practice,” Dr. Gierada said. “But it must be implemented in a responsible way that follows the guidelines to make sure it is done as safely and effectively as possible.”

Although these past studies provide a solid foundation for the clinical use of low-dose CT screening for lung cancer, the challenge of reducing morbidity and mortality from the disease is an ongoing battle. Because the majority of past studies were done in a controlled clinical setting, more information is now needed about patient outcomes with low-dose CT screening for lung cancer in routine clinical practice.

Now that CT screening is becoming more widely used in general clinical practice, it’s important that radiologists regularly assess the correctness of its implementation and ensure that the outcomes are favorable, Dr. Gierada said.

“Continued refinements in patient selection and image analysis methods may further improve the efficiency and effectiveness of CT screening,” Dr. Gierada said. “However, there is much room for other advances in prevention, risk reduction, early detection and treatment.”

For More Information

Access the Radiology: Imaging Cancer study, “Low-Dose CT Screening for Lung Cancer: Evidence from 2 Decades of Study.”

RadiologyInfo.org Offers Patient Lung Cancer Screening Information

The RSNA/ACR patient information website RadiologyInfo.org offers a roster of information for patients on lung cancer screening.

Topics include:

• What is lung cancer screening?

• Who should consider lung cancer screening – and why?

• How is lung cancer screening performed?

Patients can also access a video of Elliot K. Fishman, MD, discussing lung cancer screening and other resources at RadiologyInfo.org.