USPSTF Guidance on Screening for Lung Cancer

SUMMARY:

The current USPSTF guidelines recommend annual cancer screening using low-dose CT. Lung cancer has a poor prognosis and is the third most common type of non-skin cancer in the United States. Lung cancer is the leading cause of cancer death in men and in women. The USPSTF recommends (Grade B – offer or provide this service)

Screen annually for lung cancer with low-dose computed tomography

Discontinue screening when the patient has not smoked for 15 years or develops a health problem that substantially limits life expectancy or the ability or willingness to have curative lung surgery

Population

Adults aged 50 to 80 years who have a 20 pack-year smoking history and currently smoke or have quit smoking within the past 15 years

Risk Factors for Lung Cancer

Most important factors
- Age: Incidence relatively low in individuals under 50 and increases with age, especially >60 years
- Total cumulative exposure to tobacco smoke
- Years since quitting smoking
Additional risk factors
- Environmental exposures
- Prior radiation therapy
- Other (noncancer) lung diseases
- Family history

Screening Tests

Low-dose CT
- High sensitivity and acceptable specificity in high-risk populations persons

Balance of Benefits vs Harms

Annual screening for lung cancer with low-dose CT is of moderate net benefit in asymptomatic persons who are at high risk for lung cancer based on age, total cumulative exposure to tobacco smoke, and years since quitting smoking

KEY POINTS:

Evidence of Benefit for low-dose CT

Large RCT – National Lung Screening Trial (NLST) is cited as the study demonstrating clinical utility
Participants
- 55 to 74 years
- Cigarette smoking histories of ≥30 or more pack-years and who, if they are former smokers, have quit within the last 15 years
Results: Low-dose CT
- Reduces lung cancer mortality by 20% (95% CI, 6.8 to 26.7; P = .004)
- Reduces all-cause mortality by 6.7% (95% CI, 1.2 to 13.6; P = .02)
- Updated analysis: Lung cancer reduction of 16%

Harms
- Primarily harm is risk for false-positive low-dose CT
- Majority of positive results do not lead to a diagnosis and up to 96% of positive exams may not result in cancer detection
- In a high-quality screening program, further imaging can resolve most, although not all, false-positive results
- Overdiagnosis can be up to 30% depending on screening population per heterogenous meta-analysis (NCI)
- Radiation Exposure from CT

The NELSON Trial (NEJM, 2020)

The NELSON RTC demonstrated that at 10 years of follow-up, screening with volume CT imaging
- Reduced lung-cancer mortality by 24% among men and by 33% among women in high-risk populations
- Reduced overdiagnosis to 10%
- Improved PPV to 43.5%

Calculating Pack-Years

Calculated by multiplying the number of packs of cigarettes smoked per day by the number of years the person has smoked
- 1 pack = 20 cigarettes
Examples
- 1 pack (20 cigarettes) per day for 1 year = 1 pack-year
- 2 packs (40 cigarettes) per day for half a year = 1 pack-year
- ½ pack (10 cigarettes) per day for 20 years = 10 pack-years

Recommendations of Other Professional Societies

American Society of Clinical Oncology
- Annual screening
- People age 50 to 80 who have smoked for 20 pack-years or more
- CT screening not recommended: patients with a serious condition that could affect cancer treatment or shorten a person’s life
American College of Chest Physicians
- Annual screening
- Age 55 to 80 years with ≥20 pack-year smoking history and either continue to smoke or have quit within the past 15 years
- Use as an opportunity to discuss tobacco cessation
American Cancer Society
- Annual screening
- Age 50 to 74 years
- Have at least a 20 pack-year smoking history