- Sarah Coles, MD and Alexis Vosooney, MD
Recently the U.S. Preventive Services Task Force (USPSTF) updated its recommendation statement on lung cancer screening, lowering the age to start screening and pack year eligibility. The USPSTF now recommends annual screening for lung cancer with low-dose computed tomography (LDCT) in adults aged 50 to 80 years who have at least a 20 pack-year smoking history and currently smoke or have quit within the past 15 years. Screening should stop once a person has not smoked for 15 years or has health issues that limit life expectancy or the ability and desire to have curative lung surgery.
The American Academy of Family Physicians (AAFP) disagreed with the previous (2013) USPSTF recommendation, which was based predominantly on a single trial, the National Lung Screening Trial (NLST). At that time, the AAFP concluded there was insufficient evidence to recommend for or against LDCT lung cancer screening. The AAFP had concerns about the generalizability of the trial (conducted in a large, academic medical center with a population that was younger and more likely to be current smokers than in the general population), the uncertain magnitude of benefit and the potential for harm, overdiagnosis, and uncertainty about optimal screening intervals. Championing the science, the AAFP highlighted concerns about this recommendation and called for additional research, and that challenge was met.
The new evidence review commissioned by the USPSTF includes seven randomized clinical trials (RCTs) of lung cancer screening with LDCT. NLST and the NELSON trial were the largest and the only trials powered to detect lung cancer mortality benefits to screening. Screening resulted in a difference in lung cancer specific mortality of 0.46%. The relative risk reduction for lung cancer mortality is 16-20%. The NELSON trial demonstrated a number needed to screen (NNS) to prevent one lung cancer death of 130 over 10 years of follow up. These improvements in cancer specific mortality are comparable or greater than other recommended screening tests such as breast cancer screening. A modeling study was also performed comparing screening strategies with different starting and stopping ages, frequency, and eligibility criteria. This analysis suggested that the 2021 USPSTF recommendation would result in more benefit than the 2013 recommendation.
Among studies conducted in the US, rates of overdiagnosis and false positives varied widely, with false positives generally declining with each screening round. In NLST, false positives led to invasive procedures and complications were rare. Use of current nodule management strategies such as Lung-RADS can reduce false positive rates and decrease unnecessary invasive procedures and improve the balance of benefit and harms.
After a robust discussion that included the strength of evidence, the risk of harm, the likelihood and magnitude of benefit, and the impact on health equity, the AAFP’s Commission on Health of the Public and Science agreed that there was sufficient data from clinical trials and observational studies to recommend screening and supported the USPSTF recommendation.
Further research is needed into harms of screening, particularly rates and consequences of overdiagnosis, unnecessary procedures, and barriers to implementation in community settings. None of the included studies in the USPSTF systematic review provided estimates for the lifetime risk of radiation-induced cancers or fatal cancers from continuing annual screening up to age 80. The general population is less likely to benefit than the study participants in NSLT and NELSON trials because of higher risks of other causes of death, such as heart disease. These trials were mainly conducted at large, academic medical centers with access to case management, specialized radiologists, and surgical expertise. Community based practices may not have the same resources to navigate positive results and follow up needs. The studies had poor racial and gender diversity, and the impact of screening on health equity for communities of color is unknown.
As with all screening recommendations, family physicians should discuss the potential benefits and risks of harm with each patient when considering lung cancer screening. The National Cancer Institute has developed resources to help clinicians with these discussions. While lung cancer screening does appear to help, smoking cessation remains key to reducing lung cancer deaths.