Mortality Benefit of Lung Screening

THE BENEFITS OF LOW DOSE CT LUNG CANCER SCREENING

 

Lung cancer is the leading cause of cancer death among both men and women. In fact, more people die each year from lung cancer than colon, breast, prostate and pancreatic cancer combined. And although many improvements in diagnosis, staging and treatment have been made, long-term lung cancer survival rates remain extremely poor.

 

The major risk factors, on the other hand, are well known. 90% of all lung cancer can be attributed to smoking. That means in the US, an estimated 94 million current or former smokers have an increased risk for the disease. The huge size of this at-risk group is a major reason why there have been many efforts to find and develop an effective low dose computed tomography (CT) lung cancer screening test over the past several years.

 

Recent Advances in Low Dose CT Lung Cancer Screening

 

In the past, efforts to identify an effective screening test have been unsuccessful. Specifically, several randomized screening trials were able to detect early-stage lung cancer, but were inconclusive in showing a mortality benefit from such screening. However, recent advances in multidetector computed tomography have allowed screening studies using low dose ct scan (LDCT) to be performed. With these tests, patients are exposed to acceptable levels of radiation and only need to hold a single breath. The low radiation dose preserves the detection of focal lung lesions because of the inherently high contrast between aerated lung and soft tissue.

 

National Lung Screening Trial (NLST)

 

The question the NLST set out to answer was whether low dose CT lung cancer screening would reduce mortality from lung cancer for high-risk individuals. The NLST focused on screening people 55 to 74 years old who have cigarette smoking histories of 30 or more pack-years, and who, if they are former smokers, have quit within the last 15 years.

 

The initial NLST found that screening with low dose CT scan reduces mortality by 20% and all-cause mortality by 6.7%.


NLST Results (excerpt)
Lung cancer mortality reduction: 20%
(95% confidence interval [CI], 6.8–26.7; P = .004)


All-cause mortality reduction: 6.7%
(95% CI, 1.2–13.5; P = .02)


Study Design: Evidence obtained from a randomized controlled trial.
Internal Validity: Good


Consistency: Not applicaable (N/A) – one randomized trial to date.
External Validity: Fair

 

With these results, the NLST trial is the first randomized screening trial for lung cancer to have shown improvements in both disease-specific and all-cause mortality.

 

Conclusion

 

Despite being the number one cause of cancer death, lung cancer isn’t the most heavily researched. In fact, federal funding for lung cancer research is relatively small compared with funding for other major cancers. That’s why, with this clear conclusion that low dose CT lung cancer screening reduces mortality by up to 20%, the NLST is a major step forward in the advancement of more effective lung cancer screening programs. By increasing detection of this potentially-curable disease, low dose CT lung cancer screening can drastically change lung cancer examination and management for hospitals and patients across the country.

 

References

 

Gutierrez A, Suh R, Abtin F, Genshaft S, Brown K. Lung Cancer Screening. NCBI Website. Accessed October 16, 2018.

 

Lung Cancer Screening (PDQ) – Health Professional Version. National Cancer Institute Website. Accessed October 16, 2018.

How to Manage Ground Glass Opacifications

Ground Glass Opacifications (GGOs) can pose a variety of challenges for physicians. Below is a short guide to help ensure proper diagnosis and management.

 

What are GGOs?

 

Ground Glass Opacifications are a subset of pulmonary nodules. Unlike solid nodules, GGOs occur with non-uniformity and less density, which can cause a hazy appearance. GGOs may be non-solid (referred to as “pure ground glass”) or part-solid (part of the ground-glass opacity completely obscures the tissue). Part-solid nodules are most strongly associated with lung cancer detected in CT or other imaging modalities.

 

The risks of GGOs

 

Knowledge of the causes and effects of GGOs as well as knowledge of patient history are critical in proper diagnosis and management. In malignant part-solid GGO nodules, the solid part histologically represents invasion, whereas the pure GGO areas are considered adenocarcinoma in situ (AIS) – which is the most common cancer manifesting with ground-glass opacity on CT. Because of this, solid transformation of GGO nodules is considered a strong indicator of malignancy. GGO nodules often grow slowly, and if malignant transformation from carcinoma in situ does occur, the process may take years. This means that a longer follow-up time is necessary. Apart from malignant disease, GGO changes can represent lung infections, lung edema with fluid in the interstitium, patchy increased parenchymal perfusion, or interstitial diseases.

 

The unique challenges of GGOs

 

In patients with pure GGO nodules, tumor growth can be slow and invasive disease is uncommon. Despite this, resection rates can be high. These unique features pose a challenge for physicians and patients managing GGOs over time. Similar to the management of solid nodules, the goal with GGOs is to identify and cure (usually through resection) all dangerous cancers, and to avoid resection in all benign tumors. With GGOs, the risks of observation with serial imaging are usually lower, but the observation periods may be significantly longer in order to achieve these goals.

 

Recommended management

 

Below is a limited summary of the 2017 Fleischner guidelines for GGO and subsolid pulmonary nodules.

 

Pure GGO Pulmonary Nodules

 

For pure GGO nodules ≤5 mm in diameter, no routine follow up is suggested. For suspicious pure GGOs ≤5 mm, a CT scan should be performed at 2 and 4 years. For pure GGO nodules >5 mm in diameter, a CT scan should be performed between 6 and 12 months in order to confirm persistence, and then another CT scan should be performed every 2 years until the 5-year mark. After 5 years, the physician and patient can assume benignity and stability and stop following the nodule.

 

Part Solid (Subsolid) Pulmonary Nodules

 

A general rule is that GGO cannot truly be defined as part solid until after the nodule is larger than 6 mm diameter. For subsolid nodules less than 6mm, no routine follow up is recommended. A suspicious nodule can be followed with a 2 and 4-year CT scan. For subsolid nodules greater than 6 mm, a CT scan should be performed between 3 and 6 months to confirm persistence. If the overall nodule size does not change and the solid component remains less than 6 mm, an annual CT scan should be performed for 5 years. After 5 years, the physician can assume stability and stop following the nodule.

 

Multiple Subsolid Nodules or GGO

 

The category of multiple subsolid nodules includes both pure GGO and part solid GGO. This category can often represent infectious or inflammatory processes. In patients with multiple subsolid nodules smaller than 6 mm, an initial follow up scan is recommended at 3-6 months, with the consideration of follow up at approximately 2 and 4 years to confirm stability depending on the clinical setting. In patients with multiple subsolid nodules with at least one nodule that is 6 mm or larger, management decisions should be based on the most suspicious nodule. If persistence is confirmed on CT scan after 3-6 months, then subsequent CT scans should follow the recommendations from the category of the most suspicious nodule. If multiple nodules are 6 mm or larger, physicians should use the one that is determined to be most suspicious to guide the timing of future scans.

 

References

 

Copeland S, Islam E. Management of Ground Glass and Subsolid Pulmonary Nodules: Review. Pulm CCM Website. Accessed September 2, 2018.

 

Pedersen JH, Saghir Z, Winkler Wille MM, Thomsen LH, Skov BG, Ashraf H. Ground-Glass Opacity Lung Nodules in the Era of Lung Cancer CT Screening: Radiology, Pathology, and Clinical Management. Modern Medicine Network Website. Accessed September 2, 2018.