Colorectal cancer (CRC) poses an important challenge for public health, standing as the second-leading cause of cancer deaths in the United States. Future projections suggest a grim outlook, with CRC expected to become the leading cause of cancer-related mortality among adults aged 20-49 by 2030 [1]. Alarmingly, more than 75% of people who die from CRC are not up to date with recommended screening [2].
Screening for CRC is crucial, as early detection dramatically increases the survival rate. When CRC is diagnosed at an early stage before it has spread, the 5-year relative survival rate can be as high as 91%. However, achieving widespread screening has been negatively impacted by the invasiveness of current methodologies. Colonoscopy, considered the gold standard for CRC screening, is invasive, requires significant preparation, and can be inconvenient and uncomfortable, leading to low adherence to recommended screening guidelines. This has created an urgent need for more accessible and less invasive screening options to adherence to guidelines and early detection rates.
Stool-based screening tests for CRC
The Fecal Immunochemical Test (FIT) and the Fecal Occult Blood Test (FOBT) have been the cornerstone of non-invasive CRC screening for years. Through decades of research, including the pivotal Minnesota Colon Cancer Control Study, annual FOBT screening has been shown to reduce CRC mortality by 32% [3]. Similarly, the implementation of FIT in community-based populations has demonstrated significant decreases in CRC incidence and mortality, highlighting the utility of these tests in early detection and their contribution to reducing the disease burden [4]. More recently, Cologuard from Exact Sciences has emerged as a next-generation stool DNA test, offering a novel approach by combining the detection of altered DNA and blood in the stool, aiming to improve upon the sensitivity and specificity of traditional stool-based tests. The 20,000-participant BLUE-C study marked a significant milestone, demonstrating that Cologuard Plus, the latest iteration, exhibited a 94% sensitivity for detecting CRC, outperforming the independent FIT in overall CRC sensitivity, and showing promising results in the detection of stages I-III cancer, high-grade dysplasia, and advanced precancerous lesions [5].
However, while stool-based tests like FIT, FOBT, and Cologuard have advanced the field of non-invasive CRC screening, they present notable challenges. The requirement for stool samples can deter individuals from participating due to the inconvenience and discomfort associated with the sample collection process, impacting the overall user experience. Additionally, these tests exhibit limited sensitivity for detecting advanced adenomas—23% for FIT and 43% for Cologuard—highlighting a significant gap in early cancer and precancerous lesion detection. These limitations underscore the urgent need for continuous innovation in screening technologies.
On this front, blood-based screening tests are a promising innovation for more effective CRC screening methods. These innovative approaches aim to address the shortcomings of stool-based tests by offering a more user-friendly experience and potentially higher sensitivity for early-stage cancer and advanced adenomas.
Blood-based screening tests for CRC
The need for blood-based screening tests has been recognized by the Centers for Medicare & Medicaid Services (CMS). In a landmark decision, CMS determined that the evidence supports covering blood-based biomarker tests as an appropriate CRC screening method once every three years for Medicare beneficiaries. This decision applies when tests are conducted in a Clinical Laboratory Improvement Act (CLIA)-certified laboratory, ordered by a treating physician, and when patients meet specific criteria: they must be aged 50-85 years, asymptomatic, and at average risk for developing CRC. Furthermore, these tests must have FDA market authorization for CRC screening and demonstrate sensitivity and specificity that meet or exceed established benchmarks (74% for sensitivity and 90% for specificity) [6].
In this evolving landscape, two examples of DNA-based screening tests have come to the forefront: the Epi proColon test for detecting methylated SEPT9 (mSEPT9) and Guardant Health’s Shield test. The FDA approved Epi proColon test identifies specific DNA markers associated with CRC, providing a non-invasive option for screening. Meanwhile, the Shield test by Guardant Health represents a significant advancement, boasting 83% sensitivity and 90% specificity overall, aligning closely with the performance of other recommended non-invasive screening modalities [7]. Despite these promising metrics, both tests face challenges in detecting early-stage cancer (Clinical Stage I) and advanced adenomas with the desired sensitivity, highlighting a gap in the early detection of CRC (Shield test: sensitivity of 55% for clinical stage I CRC and 13% for advanced adenoma detection).
This limitation underscores the need for further innovation, particularly in enhancing sensitivity for early-stage cancer and advanced adenoma detection. Herein lies the untapped potential of protein biomarkers for CRC screening. Unlike current methods that rely heavily on circulating tumor DNA (ctDNA) and may not effectively detect early-stage cancers, protein biomarkers might present a novel approach for identifying CRC and advanced adenomas at a stage when treatment can be most impactful. On this front, Freenome is another notable entity advancing the incorporation of protein biomarkers for CRC screening. The company recently announced the completion of enrollment for PREEMPT CRC, its large, prospective study aimed at validating its multi-omic blood test for colorectal cancer screening among average-risk adults. Preliminary results have been promising, demonstrating a sensitivity of 94% and a specificity of 94% for detecting early-stage (I/II) CRC [8].
Protavio is pioneering this approach through its participation in the DIOPTRA EU project, aiming to discover and develop a blood-based protein biomarker panel combined with advanced computational algorithms for the detection of CRC.
Protavio and the DIOPTRA screening test
DIOPTRA is a Horizon Europe project for the mission on cancer that aims to revolutionize CRC screening through the development of novel methods and tools for risk assessment and early detection (GA#101096649). At the heart of the DIOPTRA project is Protavio’s commitment to leverage our expertise in protein-based biomarkers. Our goal is bold yet straightforward: to discover and develop an in vitro diagnostic (IVD) protein biomarker panel that serves as a reliable CRC screening tool, capable of identifying the disease at its early stage.
Our strategy encompasses a discovery pipeline for the analysis of matched blood and tissue samples across four distinct groups: healthy individuals, those with non-advanced adenomas, those with advanced adenomas, and CRC patients, primarily at early stages. Using the Olink Explore platform, we quantify the expression of 3,000 protein biomarkers in blood samples, aiming to discover biomarkers that distinctly differentiate between these groups. Concurrently, matched tissue samples undergo analysis through NGS transcriptomics, allowing us to uncover the CRC mechanism and construct a robust protein-protein interaction (PPI) network to help prioritize markers directly associated with the disease’s onset and progression.
The culmination of this discovery process is a panel of blood-based protein biomarkers with the potential to detect advanced adenomas and early-stage CRC with unparalleled sensitivity and specificity. This panel is then developed into a multiplex assay on the Luminex platform, where our expertise shines in identifying optimal antibody pairs and ensuring the assay’s analytical performance through ISO13485-compliant procedures. A large-scale pilot study across eight EU clinical sites is pivotal to our efforts. It involves collecting blood samples and corresponding clinical data, with colonoscopy diagnosis serving as the gold standard. Our objective is to rigorously assess the clinical performance of our multiplex assays, focusing on their sensitivity and specificity, particularly in detecting advanced adenomas and early stage CRC [9].
The DIOPTRA project stands at the forefront of a paradigm shift in CRC screening. By harnessing the potential of protein biomarkers, we’re not just developing a tool for early detection; we’re working towards a future where CRC can be identified promptly, treatment can begin sooner, and lives can be saved.
References
[1] American Cancer Society: Colorectal Cancer Key Statistics. www.cancer.org/cancer/colon-rectal-cancer/about/key-statistics.html
[2] Doubeni CA, Fedewa SA, Levin TR, et al. Modifiable Failures in the Colorectal Cancer Screening Process and Their Association With Risk of Death. Gastroenterology 2019;156:63–74.
[3] Mandel, Jack S., et al. “Reducing mortality from colorectal cancer by screening for fecal occult blood.” New England Journal of Medicine 328.19 (1993): 1365-1371.
[4] Levin, Theodore R., et al. “Effects of organized colorectal cancer screening on cancer incidence and mortality in a large community-based population.” Gastroenterology 155.5 (2018): 1383-1391.
[5] Imperiale, Thomas F., et al. “Next-generation multitarget stool DNA test for colorectal cancer screening.” New England Journal of Medicine 390.11 (2024): 984-993.
[6] https://www.cms.gov/medicare-coverage-database/view/ncacal-decision-memo.aspx?proposed=N&NCAId=299
[7] Chung, Daniel C., et al. “A Cell-free DNA Blood-Based Test for Colorectal Cancer Screening.” New England Journal of Medicine 390.11 (2024): 973-983.
[8] Putcha, Girish, et al. “Blood-based detection of early-stage colorectal cancer using multiomics and machine learning.” Abstract presented at: the American Society of Clinical Oncology (ASCO) GI Symposium. 2020.
[9] ISRCTN15583857 https://doi.org/10.1186/ISRCTN15583857 Early screening for colorectal cancer via a simple blood sample