Every year, millions of people are diagnosed with cancer, and once the disease is detected in an advanced stage, the chances of successful treatment decline significantly. Although traditional screening methods—such as mammography for breast cancer, colonoscopy for colorectal cancer, and Pap smears for cervical cancer—remain effective for early detection, developing and widely implementing separate tests for each type of cancer presents economic and logistical difficulties. Consequently, the approach known as “multi-cancer early detection” (MCED), which aims to identify multiple cancers simultaneously through a single blood sample, is gaining increasing attention. MCED tests can detect several tumors with just one blood draw, thereby enhancing patient comfort. Moreover, they may fill a critical gap by enabling painless and early cancer detection, particularly in cases where conventional methods are insufficient. To date, screening programs have been conducted for various cancer types, yet many remain unscreened and continue to cause high mortality rates due to late diagnosis. In this sense, MCED is seen as a promising approach that could help detect and treat tumors in their early stages, even before symptoms appear.
In particular, research initiatives and corporate collaborations in the United States are concentrating on developing MCED tests that screen for biomarkers such as cell-free DNA (cfDNA) in the blood, with the goal of identifying tumors before they manifest clinical signs. Studies like DETECT-A and Pathfinder indicate that although these tests show considerable potential, there are still various uncertainties to be resolved. Nevertheless, preliminary data suggest that MCED tests could offer a promising alternative and, over time, may serve as a complementary option alongside traditional screening methods.
Searching for Multiple Cancers in a Single Tube of Blood
In the DETECT-A study, conducted with more than 10,000 women, the positive predictive value (the percentage of truly detected cancer cases) reached 28%. In the Pathfinder study, which examined the test known as “Galleri” developed by the company Grail, this figure rose to as high as 38%. Although these numbers might initially appear low, the fact that the false-positive rate (testing positive when no cancer is actually present) remains below 1% is regarded as a significant achievement. In more traditional screening methods, this rate can be higher, often causing unnecessary anxiety for many individuals.
Another notable feature of these new tests is their attempt to predict the specific tissue or organ where the cancer originates. For example, Galleri analyzes DNA methylation profiles not only to identify the presence of a cancer signal, but also to determine the tumor’s possible location in the body. Meanwhile, Exact Sciences’ “Cancerguard” test incorporates cfDNA analysis alongside certain protein biomarkers, such as the prostate-specific antigen (PSA) for prostate cancer. Theoretically, this allows many different cancer types to be screened simultaneously from a single blood sample.
Advantages and Concerns
MCED tests primarily stand out for their ability to detect multiple types of cancer simultaneously from a single blood sample, thereby enhancing patient comfort. In cases where traditional screening methods prove insufficient, they are thought to fill a significant gap by detecting asymptomatic cancers at earlier stages. Moreover, by potentially identifying cancers that current screening programs do not cover—those often diagnosed late and associated with high mortality rates—MCED is seen as a promising tool to address this oversight.
However, because early-stage cancer cells release only small amounts of cfDNA, certain cancer types might be missed. Although relatively rare, false-positive results can still lead to unnecessary anxiety and additional expenses. In the event of a positive test, it is not yet fully clear which advanced diagnostic or imaging procedures should be performed next. Correctly answering the question “Which tissue is generating the cancer signal?” is crucial to protect patients from unnecessary interventions.
Comprehensive Clinical Trials and Future Outlook
Evaluating MCED tests requires not only measuring their ability to detect cancer signals but also determining whether they can improve long-term survival rates and quality of life. To this end, large-scale research initiatives are underway in different countries. The goal is to clarify which MCED test provides the most benefit for which patient group and under what circumstances.
According to current literature, it is unlikely that MCED tests will completely replace traditional screening methods in the near term. Rather, they are increasingly seen as an additional screening option in clinical practice. For example, the fact that the Galleri test is now prescribed to certain patients in the United States to gather “real-world” data highlights the growing interest in this area. However, the lack of approval from the U.S. Food and Drug Administration (FDA) and the absence of insurance coverage mean that the widespread implementation of these tests is dependent on regulatory and economic factors. The acceptance and availability of these tests on a global scale (including Turkiye) will take place after they undergo trial and validation phases. Patients or physicians seeking to benefit from MCED tests on an individual basis can consider contacting centers abroad where such services are currently offered.
High Expectations, Waiting on the Science
Early cancer detection remains a high priority in medicine, and multi-cancer early detection tests hold considerable potential in this arena. The ability of patients and clinicians to correctly interpret test results, followed by timely and effective additional diagnostic steps, will help determine—especially once comprehensive clinical research data are integrated—whether MCED tests can genuinely save lives.
At present, it should be remembered that MCED approaches can only achieve the status of “gold standard” diagnostics through appropriate standardization and robust scientific evidence. Collaborative efforts by government agencies and healthcare professionals to ensure the proper use of these tests will help maximize the vital benefits provided by early detection.
References:
Buchanan, Adam H et al. “Multiyear Clinical Outcomes of Cancers Diagnosed Following Detection by a Blood-Based Multicancer Early Detection Test.” Cancer prevention research (Philadelphia, Pa.) vol. 17,8 (2024): 349-353. doi:10.1158/1940-6207.CAPR-24-0107
Feng, Xiaoshuang et al. “Cancer Stage Compared With Mortality as End Points in Randomized Clinical Trials of Cancer Screening: A Systematic Review and Meta-Analysis.” JAMA vol. 331,22 (2024): 1910-1917. doi:10.1001/jama.2024.5814
Cirillo, Nicola. “Deceptive Measures of “Success” in Early Cancer Detection.” Current oncology (Toronto, Ont.) vol. 31,9 5140-5150. 30 Aug. 2024, doi:10.3390/curroncol31090380
Samimi, Goli et al. “Primary care physicians and laypersons’ perceptions of multicancer detection clinical trial designs.” JNCI cancer spectrum vol. 8,5 (2024): pkae084. doi:10.1093/jncics/pkae084
Milner, Danny A Jr, and Jochen K Lennerz. “Technology and Future of Multi-Cancer Early Detection.” Life (Basel, Switzerland) vol. 14,7 833. 29 Jun. 2024, doi:10.3390/life14070833
