A session chaired by ASCO and ESMO leadership included experts on the latest lung and colorectal cancer screening technologies and persistent disparities in screening access and uptake.
While there has been significant progress in lung and colorectal cancer screening technology, disparities in screening uptake and access to care continue to impact outcomes among different populations, according to presenters in a session at the 2023 American Society of Clinical Oncology (ASCO) Annual Meeting.
The session, a joint endeavor between ASCO and the European Society for Medical Oncology (ESMO) was chaired by current ASCO president Eric P. Winer, MD, of Yale Cancer Center; current ESMO president Andres Cervantes, MD, PhD, of the University of Valencia; and ASCO scientific program chair Kimmie Ng, MD, MPH, of Dana-Farber Cancer Institute.
“We decided to focus on 2 of the leading causes of cancer mortality for which there is evidence to support screening, and also because there are different recommendations for screening for these cancers in different countries around the world,” Winer said.
Presenters included Folasade May, MD, PhD, MPhil, director of the May Laboratory at the University of California Los Angeles; Christophe Von Garnier, MD, of Centre Hospitalier Universitaire Vaudois; Cary Philip Gross, MD, professor of medicine and public health at the Yale School of Medicine; and Charles Swanton, MD, PhD, FRCP, a clinician scientist the Francis Crick Institute.
Screening and Barriers in Colorectal Cancer
May kicked off the session with an overview of the evidence supporting colorectal cancer screening, the 2021 United States Preventive Services Task Force (USPSTF) colorectal cancer screening guidelines, screening utilization in the United States, and barriers to screening. Colorectal cancers, she noted, are the third most common cause of cancer and the second most common cause of cancer-related deaths in the United States—but 1 in 3 adults do not undergo screening.
Randomized trials and observational data support the efficacy of a variety of screening methods, May noted. Additionally, the rate of early-onset colorectal cancer has risen in recent years, with patients aged 20-49 showing a 51% increase in colorectal cancer incidence, while rates have declined in those 50 and older. This finding was a catalyst for new USPSTF screening guidelines in 2021, which recommend screening for those aged 45-49 years in addition to those aged 50-75.1
A range of screening modalities can be employed, including stool-based tests such as fecal immunochemical assessments and direct visualization techniques such as virtual colonography or colonoscopy. But any non-colonoscopic methods require colonoscopy as a second step to complete screening—a step only about half of patients take, May said. Other non-invasive strategies, such as new stool-based tests, blood-based multicancer early detection (MCED) tests, wireless capsule endoscopy, and urine-based screening.
A major challenge is that historical gaps in screening rates tied to social determinants of health such as race, ethnicity, education, or socioeconomic status have not fully closed, May noted, adding that implementation science often focuses on disadvantaged groups.
“In addition to patient-level factors like lack of knowledge, cultural differences, health literacy, language, distrust in the health care system, there are also invertible provider-level, system-level, and policy-level factors,” May said. “So, we do need to focus on increasing awareness among providers, making sure that all providers are recognized for our populations—as of now, there are data that demonstrate there are some biases in who we recommend screening to.”
In mitigating disparities, Gross noted the importance of centering marginalized communities in screening implementation research and guidance, employing learning health systems, taking a public health perspective on screening, and community engagement are all strategies that may improve screening implementation and outcomes, according to Gross.
“As far as the overarching strategies, it's really important that we invest in research that will help us to identify the best strategies to mitigate disparities. We need to allocate resources in a very different way, both within our health system and outside our health care system, because people have competing demands [and] competing risks that can also impede their ability to undertake cancer screening,” Gross said.
Cancer screening must also be part of a comprehensive approach to mitigate disparities, not examined in a vacuum, he said. Gross also emphasized the importance of community-based participatory research to increase the reach of screening and give communities a voice in the best approach to screening implementation.
Lung Cancer Screening Evidence and Disparities
Garnier discussed guidelines and emerging evidence for lung cancer screening, as well as the challenge of reaching underserved patients. He opened with an overview of the screening process, which currently includes low-dose chest CT screening.
Evidence is still emerging in the lung cancer screening space, he noted, with the majority of data coming from 2 large trials: the National Lung Screening Trial in the United States2 and the NELSON trial in the Netherlands and Belgium.3 Several smaller trials also contribute to the evidence for lung cancer–related mortality reduction with lung cancer screening.
Reaching at-risk populations can also be a challenge, and various approaches have been taken to reduce the barriers to screening. Garnier highlighted an initiative in the United Kingdom, the Manchester Lung Health Check, that brings screening to areas with high disease prevalence by screening patients in mobile units and has facilitated substantially higher uptake and adherence compared with individuals in the United States.
In Switzerland, an implementation group of various stakeholders emphasized the importance of positive framing as a lung health check, a broad-based invitation of risk population, primary care provider involvement, and centers or mobile units serving as one-stop clinics. High-risk patients are often fearful, socioeconomically deprived, culturally or geographically isolated, and less likely to comply with health care, Garnier noted.
“An important lesson from the Manchester trial is that there shouldn't be initial mention of lung cancer or smoking cessation, that there should be broad information in all potential contact areas—pharmacies, [general practitioners], hospitals, shopping areas, and public toilets,” Garnier said. “Also, social medias should be used as much as possible, and family and friends involved in a process of screening. Videos of processes can be important to decrease anxiety, and employing celebrities to try and get the message across about lung cancer screening is important.”
Novel Screening Approaches in Lung and Colorectal Cancers
Swanton spoke to principles behind the latest screening technologies and considerations for the future of both lung and colorectal cancer screening.
He first discussed the challenges of detecting circulating tumor DNA (ctDNA), which he likened to a needle in a haystack in the context of early-stage lung cancer detection because so little ctDNA is present in early cancers. Lowering the limits of ctDNA detection will be an important area of research, he said.
Multiple studies have shown that ctDNA is associated with aggressive tumor biology and poor clinical outcomes, Swanton noted, adding that tumors not shedding ctDNA or only shedding small amounts of ctDNA screening are associated with better outcomes.
Swanton raised the issue of the potential for overdiagnosis, which is often raised in the context of ctDNA testing for early-stage cancers. However, he does not consider this to be a significant risk. “The reason for that is that cDNA allelic fractions are essentially independently prognostic of tumor stage. The more you release, the worse the outcome, and ctDNA itself is a poor prognostic indicator.”
In colorectal cancer, another challenge is that an estimated two-thirds of the benefit of colonoscopy can be attributed to the detection of adenomas, which are rarely ctDNA positive, Swanton said. Across cancer types, the use of ctDNA testing would ideally complement screening methods already known to be effective, he added.
There is still a case for MCEDs, which ideally would detect multiple cancers without sacrificing sensitivity and specificity. This could help mitigate the issue of poor screening uptake for individual cancers, which Swanton noted only compounds with the number of screenings a patient is eligible for. MCEDs optimized for specificity also have potential to reduce cumulative false positive rates compared with multiple single-cancer screenings.
“New technologies require extensive, population-based prospective studies to validate them, accounting for ethnic diversity and low socioeconomic and at-risk groups,” Swanton said.
1. Davidson KW, Barry MJ, Mangione CM, et al, for the US Preventive Services Task Force. Screening for colorectal cancer; US Preventive Services Task Force recommendation statement. JAMA. 2021;325(19):1965-1977. doi:10.1001/jama.2021.6238
2. Aberle DR, Adams AM, Berg CD, et al, for the National Lung Screening Trial Research Team. Reduced lung-cancer mortality with low-dose computed tomographic screening. N Engl J Med. 2011;365(5):395-409. doi:10.1056/NEJMoa1102873
3. De Koning HJ, van der Aalst CM, de Jong PA, et al. Reduced lung-cancer mortality with volume CT screening in a randomized trial. N Engl J Med. 2020;382(6):503-513. doi:10.1056/NEJMoa1911793