Lung cancer screening is a new standard of care

As appeared on MDatl.com.

Improving lung cancer outcomes through screening and early detection

Lung cancer remains the No. 1 cause of cancer-related death in the United States, accounting for almost 25% of all cancer-related deaths (more than colon, breast and ovarian cancers combined). Further, most cases of lung cancer present at an advanced stage when available treatments are less effective and expected mortality is markedly higher.¹ Therefore it is imperative that lung cancer is detected early. 

In 2011, the National Lung Cancer Screening Trial (NLST) demonstrated that computed tomography (CT) screening followed by two annual screens compared to standard lung X-ray reduced lung cancer mortality by 20% in individuals at high risk for developing lung cancer.² 

Furthermore, NLST findings suggest that if the U.S. population was subjected to similar enrollment criteria, an estimated 12,000 annual premature deaths due to lung cancer would be prevented through lung cancer screening.³ The result was a new standard of care in the early detection of lung cancer. Subsequently, Medicare and most third-party payers currently provide full coverage for lung cancer screening (LCS) based on NLST standards. (See Table 1.) 

Selection of Individuals for Lung Screening
In light of the NLST findings, guidelines have primarily emphasized annual lung screening eligibility based on age (55-74 years) and tobacco history. Additionally, experts agree that screenings should be discontinued once a person develops a health problem that substantially limits life expectancy or the ability/willingness to undergo definitive treatment. 

There has been much debate regarding the benefits of screening outside of the inclusion criteria used in NLST. Consequently, recommendations for screening by professional and governmental agencies have also been varied. In the decade since NLST was published, extensive additional data (including randomized controlled trials and statistical analysis) have demonstrated that many other individuals who would have been otherwise excluded from NLST would regardless have a similar risk for the development of lung cancer.⁴ While NLST was of monumental importance in establishing the role of screening, it failed to assess other risk factors including occupational exposure, family history, cancer history, race and other preexisting lung diseases such as emphysema and pulmonary fibrosis.  

Uncertainty regarding strict adaptation to NLST enrollment criteria has remained. For example, approximately 10% of lung cancer-related mortality is attributable to patients aged 45-54 (ages below the threshold studied in NLST). Conversely, functional status and comorbidities may be a more important factor than an absolute upper age limit alone. 

Likewise, the arbitrary nature of the 15 year cut off from smoking cessation is also controversial. While lung cancer risk does decrease with time following cessation, no substantial drop-off is observed in lung cancer risk at 15 years.⁵ Subsequently, investigators from The Dutch-Belgian Randomized Lung Cancer Screening Trial (Dutch acronym: NELSON study) addressed some of these clinical concerns with expanded enrollment criteria. NELSON included patients beginning at age 50, and with a lower pack/year smoking history (18.75).  

These patients were followed over a 10-year period, and despite less restrictive criteria, a tremendous survival advantage was again demonstrated for the CT screening group.⁶ NELSON confirmed the efficacy of LCS among a smoking population in reducing lung cancer-related mortality. 

The role of race should be of additional clinical concern for physicians practicing in the Atlanta metropolitan area given local demographics. While white male smokers consume 30-40% more cigarettes than their Black counterparts, Black male smokers are 34% more likely to develop lung cancer. Furthermore, Black women smoke less on average than white women, yet have similar incidence rates.⁷ Finally, African Americans have substantially higher mortality from lung cancer.⁸ Therefore, screening may be an even more powerful tool in preventing lung cancer-related death among this at-risk population. Further study will be needed to confirm this finding given the relatively low participation of Blacks in lung cancer screening studies thus far. However, screening for lung cancer remains a markedly underutilized resource despite proven efficacy across all populations. 

Barriers to Lung Cancer Screening
Across the United States, it’s estimated that under 50% of practicing primary care providers order LCS and fewer than 3-16% of eligible patients undergo LCS. A 2017 survey to study the prevalence of discussion about LCS between patients and healthcare providers in the U.S. revealed 10% of former and 18% of current smokers received any associated counseling.⁹ Despite nearly 10 years since NLST, an even more recent survey detected only 14.4% of eligible patients had been screened.¹⁰ One can easily assume the effects of the COVID-19 pandemic have further depressed LCS enrollment as substantial reductions in primary care visits and screening procedures overall has been widely reported during the pandemic. 

The most common reason given for low enrollment of patients into LCS programs is that many providers remain unaware or uninformed on the benefits of these scans. Some providers may continue to harbor nihilistic attitudes towards smokers or smoking-related lung disease. Others believe the best lung cancer prevention is smoking cessation, and subsequently, these advocates feel resources should be more focused on smoking cessation counseling. 

Of note, such counseling is a mandated component of LCS enrollment. Although prevention of smoking and smoking cessation remain among the most important interventions to prevent lung cancer, the majority of patients who die from lung cancer are former smokers, and thus will not benefit from primary prevention. 

Despite a consistent decline in national smoking rates, until recently the overall mortality of lung cancer had remained stable. Only since the era of LCS has significant improvements in lung cancer mortality been observed. This observation highlights the importance of secondary prevention including LCS. 

Other barriers to the implementation of screening include the time constraints needed to discuss/perform Shared Decision Making (SDM) and smoking cessation counseling. SDM is a requirement mandated by Centers for Medicare and Medicaid (CMS) for the approval of a LCS study. 

Unlike breast and colon cancer screening, a patient’s physician must approve the patient for a lung cancer screening exam during a shared decision-making visit. SDM broadly refers to the requirement of ordering physicians to provide a detailed risk-benefit analysis to each patient before ordering the LCS study. SDM should include a discussion of radiation exposure, the potential for unnecessary follow-up procedures and/or other diagnostic studies. In actuality, these risks may be grossly overstated. 

Advancements in Lung Cancer Screening
Significant upgrades in the technical aspects of LCS have occurred since NLST was initially published. Improvements include enhanced imaging acquisition equipment, the development of advanced interpretive guidelines and an evolved understanding of the natural history of abnormal findings. Collectively these upgrades have benefitted LCS patients by decreasing potential risks while maintaining the associated benefits. 

Early in the evolution of LCS, many critics emphasized the potential risk for significant iatrogenic radiation exposure due to repeated CT imaging. However, as the technology of CT imaging has been upgraded, the associated necessary radiation required to perform LCS has substantially decreased to levels that approach routine mammography. (See Table 2 to further place LCS radiation exposure into context.) In addressing the radiation risk relative to lung cancer screening, a position statement issued by the Health Physics Society noted: 

“There is substantial and convincing scientific evidence for health risks following high dose exposures. However, below 50-100mSV (which includes occupational and environmental exposures), risk of health effects are either too small to be observed or nonexistent.” 

Furthermore, the development of Lung-RADS (a quality assurance tool to standardize LCS reporting and management recommendations) has greatly reduced false-positive rates. As a result, fewer follow-up surveillance studies and invasive procedures including biopsies are subsequently needed. An additional important finding in the NELSON trial was a much improved false-positive rate compared to the initial NLST. This rate is very favorable when compared to other screening studies such as mammography. 

NLST and NELSON also confirmed the importance of adherence to follow-up. The survival benefit of LCS is strongly correlated with the longitudinal assessment of abnormal findings. One should not consider LCS as equivalent to an occasional or intermittent CT scan, and the importance of continued surveillance cannot be overstated. 

There must be a reliable mechanism in place to ensure follow-up of screening results and communication of results to both ordering providers and patients. Patients should be referred to an approved imaging facility that submits data to a CMS-approved registry, which employs qualified radiologists to interpret the study. Lung cancer screening is a potentially lifesaving intervention when implemented with evidence-based protocols and reliable infrastructure. 

USPSTF Recommends Changes in Criteria for Lung Cancer Screening Eligibility
The United States Preventive Services Task Force (USPSTF) has recommended a major increase in the number of Americans eligible for screening for lung cancer, saying “expanded testing will save lives and especially benefit Black people and women.” (See Table 3.) The expert panel said, “People with a long history of smoking should begin receiving annual low-dose CT scans at age 50, five years earlier than the group recommended in 2013.” USPSTF “also broadened the definition of people it considers at high risk for the disease.” 

The updated recommendations were published in JAMA.¹¹ The USPSTF’s new recommendations are expected to greatly increase access of former smokers who are advised to undergo annual screening for lung cancer. Further, it is expected that many more African-Americans and women than in the past will subsequently have access to LCS.

1. http://seer.cancer.gov/statfacts/html/lungb.html
2. NEJM 2011; 365:395-409.
3. Ma J, et al. Cancer. 2013; 119(7):1381-1385.
4. PLOS Med 2014; 11:1-13.
5.  J Med Screen. 2015 Sep;22(3):151-7.
6. N Engl J Med 2020; 382:503-513
7. https://www.cdc.gov/tobacco/data_statistics
8. https://www.cancer.org/content/dam/cancer-org/research/cancer-facts-and-statistics
9.  J Cancer Educ. 2020 Aug;35(4):678-681.
10. Am J Prev Med. 2019;57(2):250-255.
11. JAMA March 9, 2021 Volume 325, Number 10: 962-970.