The National Lung Screening Trial demonstrated that low-dose CT screening significantly reduces risk of death from lung cancer among high risk individuals.
Of course, a screening program is only one part of a complete solution aimed at decreasing the incidence and societal impact of lung cancer. Smoking cessation is clearly the main ingredient, without which lung cancer will continue to remain the greatest cancer killer worldwide and, specifically for this commentary, in the United States.
Quotes are excerpted from an article entitled "Lung Cancer Screening," by Gutierrez et al., Seminars in Interventional Radiology, vol. 30, No. 2; 2013; pp.114-120.
"In the United States, smoking prevention and cessation programs have decreased smoking rates and lung cancer mortality. However, an estimated 94 million current and former smokers remain at elevated risk for the disease.... Survival rates are stage dependent, where five-year survival for stage 1A lung cancer is 52.2% versus 3.7% for stage IV disease; most patient present with advanced disease."
"Screening is the periodic examination of a population to detect early-stage asymptomatic disease with the goal of decreasing mortality and increasing survival." Potential benefits and harmful effects to the individual and the population must be balanced in order for a screening program to be successful.
In order to "determine whether screening with low dose CT (LDCT) compared with chest radiography would reduce mortality from lung cancer among high risk individuals," the National Cancer Institute funded the National Lung Screening Trial (NLST). The trial enrolled 53,454 participants "of comparable gender proportions and smoking intensity" to the general population. however, the trial group "tended to be former smokers, younger and more educated than the comparable U.S. eligible population, which made them slightly healthier overall." Participants were randomized to receive either LDCT or chest x-ray (CXR) annually for three screens. A total of 24.2% of CT screens and 6.9% of CXR screen were positive in the trial."
"The NLST found that annual LDCT screening benefits individuals at high risk for lung cancer with a reduced relative risk of death from lung cancer by 20% and reduced absolute risk by 0.33%."
"Potential harmful effects of lung cancer screening include radiation-induced cancers, over-diagnosis, and high false-positivity rates."..."In smoking women, annual LDCT screening conferred a 0.85% radiation-related risk of developing lung cancer in addition to the population-based expected risk of 17%, a 5% increase in risk. In smoking men, annual LDCT screening conferred a 0.23% radiation-related risk of developing lung cancer in addition to the population-based expected risk of 16%, a 1.5% increase in risk." Since the trial, however, diagnostic images are generated using lower exposures. Calculations used in the trial therefore likely overestimate radiation risk. In addition, the 20% reduction in the relative risk of death more than outweighs these estimated radiation-related increases in risks.
"The NLST provides the randomized controlled trial evidence of the benefits of LDCT screening for lung cancer relative to the risks."
Lung cancer screening is effective and confers distinct benefits and low risks when the appropriate population is screened and when there is appropriate management of indeterminate lung nodules.
Screening programs must incorporate responsibility for patient communication of findings and management of appropriate follow-up. If you are a high risk individual, ask your doctor about smoking cessation programs and low dose CT screening which may be available in your area. It is never too late to get on the road to healthy living.
Summary of low-dose CT lung cancer screening recommendations:
- Low-dose CT screening for those who meet the National Lung Screening Trial criteria:
- Current or former smokers
- 55-74 years of age
- 30 pack years
- No history of lung cancer
- Emphasis of smoking cessation for patients who undergo screening
- Do not use chest x-rays for lung cancer screening
- Does not recommend universal lung cancer screening at this time
- Develop a toolkit that provides patients with lung disease a comprehensive framework of the lung cancer screening process
- Hospitals and screening centers should:
- Establish ethical policies for advertising and promoting screening programs
- Fully educate the public about lung cancer, its risks and prevention, and the importance of patient/physician discussions
- Screening should be linked to "best practice" multidisciplinary teams that can provide the needed follow-up for evaluation of nodules.