Lung Cancer: Screening with Low-Dose CT

MedicalResearch.com Interview with:
Linda L. Humphrey, M.D., M.P.H.
Professor of Medicine
Informatics and Clinical Epidemiology and Public Health for Oregon Health & Science University;Associate Chief of Medicine at the Portland VA Medical Center

Dr. Humphrey comments on this important study on
Screening for Lung Cancer With Low-Dose Computed Tomography:

Lung cancer is the 3rd leading cause of cancer in the United States and the leading cause of cancer related death.  It is estimated that in 2012 there were 226,160 cases of lung cancer and 160, 340 lung cancer related death in the US.   In addition, lung cancer is the leading cause of years of life lost to cancer.   Cigarette smoking is by far the leading cause of lung cancer in the US and while many people have quit smoking, data in the US indicate that 37% of adults are either current or former smokers and at risk of lung cancer.   

Our review evaluated existing literature evaluating screening for lung cancer with low dose computed tomography (LDCT) and found 3 studies that contribute to the literature base.  One study, the National Lung Screening Trial, conducted in the US found that among 55-74 year old men and women with at least 30 pack years of smoking and if former smoker,  had quit within 15 years, randomized to LDCT for 3 years versus chest x-ray for 3 years, lung cancer mortality was reduced by 20% and all-cause mortality by 6.7%.   We identified 2 other fair quality trials that didn’t show benefit although one, conducted in a high risk population suggested benefit and one conducted in a lower risk (for lung cancer) population did not show benefit and suggested harm.  We also evaluated existing literature outside of these trials to determine other outcomes of lung cancer screening.  We found that radiation exposure per LDCT ranges 0.8-1.5 mSV (for comparison mammograms are on the order of 0.8 mSv), that there are many false positives that require further evaluation, usually with imaging but sometimes with biopsy or surgery and that there appears to be little impact on psychological outcomes or smoking behavior.  In addition, there is what appears to be a small risk of over-diagnosis of lung cancer (meaning identifying lung cancer that won’t impact a person’s life) and many other chest findings such as coronary artery calcification and emphysema are also identified.

The clinical implications of this review are that the Task Force will be making new recommendations for lung cancer screening in the near future and that many other organizations are now recommending that individuals with 30 pack years of smoking who are either current or former (quit within 15 years)  who are ages 55-74 and sufficiently healthy enough to undergo treatment of lung cancer if it is diagnosed be screened with LDCT in systems of medical care that are well equipped for handling the treatment and diagnosis of lung cancer. The NLST also has shown that those at greatest risk of lung cancer based on medical history and age, seem to benefit the  most from screening and it will be very important that physicians are cautious in not extrapolating data on benefit to populations at lower risk of lung cancer.

Citation:

Screening for Lung Cancer With Low-Dose Computed Tomography: A Systematic Review to Update the U.S. Preventive Services Task Force Recommendation

Linda L. Humphrey, Mark Deffebach, Miranda Pappas, Christina Baumann, Kathryn Artis, Jennifer Priest Mitchell, Bernadette Zakher, Rongwei Fu, Christopher G. Slatore; Screening for Lung Cancer With Low-Dose Computed Tomography: A Systematic Review to Update the U.S. Preventive Services Task Force Recommendation.
Annals of Internal Medicine. 2013 Jul

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