An emerging technology seeks to help revolutionize the world of oncological screening: early detection tests for multiple cancers (MCED) aim to identify signs of different types of cancer from a single blood draw or other body fluid sample.
These MCED tests, a specific type of liquid biopsy, look for anomalies that may indicate the presence of cancer, such as circulating tumor DNA; some can indicate the probable origin of a cancer, while others are limited to show that it can exist cancer, without identifying a likely type or location.
A key advantage of MCEDs, advocates say, is the potential to identify cancers. in earlier and more treatable stages. As such, they could help save lives.
diagnoses in stages I, II and III (by 10%, 20% and 34%, respectively).
Os Stage IV diagnoses, on the other hand, decreased almost in half. The study authors, some of whom are employees of Exact Sciences, suggested that this demonstrates that MCED tests could detect cancer earlier of it reaching its most advanced stages, especially in types of cancer that do not have routine screening.
asymptomatic individuals without risk factors clear can lead to unnecessary exams and procedures.
It is the case that H. Gilbert Welch can detect indolent cancers — which would rarely cause symptoms or death.
In turn, this may result in unnecessary treatmentsincreasing healthcare costs and anxiety for patients.
MCEDs can also be less sensitive in detecting cancers at early stages, compared to other specific tests for certain organs, which raises doubts about whether screening with MCED actually translates into increased patient survival.
As MCED sensitivity rates — the proportion of cases in which a test correctly detects cancer — can bebe as low as about 20%although they vary greatly depending on the type of cancer and the specific test used.
MCED tests still have a high specificitythat is, the ability to correctly identify people without cancer. But, when screening a large and mostly healthy population, even a very specific test can generate numerous false positives.
In turn, this effect can lead to what clinical experts call “diagnostic odyssey“, which involves blood tests, imaging tests and additional biopsies to reach a correct diagnosis.
In one of 2023, 62% of positive results were falseno cancer was found after an exhaustive investigation.
Could it be, then, that more screenings are turning mostly healthy people, sometimes nicknamed “worried healthy people”, in sick people? It’s possible.
The late University of Pennsylvania professor of medicine William Kissick wrote one day that “a healthy individual can be defined as someone who was insufficiently studied“. This aphorism meets the idea that, the more you look for a diseasemore cases may be found.
The is a prominent example. The product’s manufacturer, Grail (which says they could get cancer by 2023), says the test can screen for more than 50 types of cancerat a list price of $949.
Grail says it has sold 185,000 tests in 2025.
Contrary to the concerns of some experts, one on MCED, recently pre-published in medRxivsuggests that these tests have a risk relatively low overdiagnosis.
The researchers looked for possible indolent cancersof slow progression, which would normally remain undiagnosed without screening. They concluded that between 2% and 6% of all cancers detected annually screened with an MCED could be overdiagnosisalthough the risk increased markedly with a person’s age.
But these conclusions resulted from a simulation; the study did not involve real people. Currently, several are underway to evaluate MCEDs that include trial participants.
influences early detection of cancer and the reduction of diagnoses in late stages. The study is sponsored by Grail.
The standard of excellence for evaluating oncological screening programs would be a independent clinical trialrandomized and controlled. A British National Health Service (NHS) study of Galleri was the first of its kind to involve an MCED.
MCED use translates into fewer deaths from cancer thanks to earlier diagnoses.
However, Galleri did not achieve the main objective from the NHS trial, which was a reduction in diagnoses at later stages of cancer.
In an email sent to Undark, Welch argued that detection of tumor DNA “may be clinically useful as a diagnostic test should not be used as a “screening test in the general population“.
Andrew Vickersbiostatistician at Memorial Sloan Kettering Cancer Center, says that “It’s a very exciting prospect be able to do just a blood test and find all cancers“, because it means that it is not necessary to test one type of cancer at a time, as with a mammogram, a colonoscopy or a lung CT scan.
But “we should not use tests unless it is proven that work”, highlights Vickers.
The problem with MCEDs, he added, is that It’s not even proven yet that detect cancers with adequate sensitivity and specificity, or that save lives.
The recent failure of the Galleri test illustrates the problem, says Vickers: “I have a big problem with companies that advertise expensive tests to the public and to prove it.”
In response to this criticism, a Grail spokesperson sent Undark a response defending the company’s product, highlighting its ability to screen for many different types of cancer, “including hard-to-detect cancerssuch as those in the pancreas, ovary and liver, before becoming symptomatic”.
Regarding the recent failure of the trial, Grail’s response states that, although “no reduction in the main objective has been observed
Steven Woloshinprofessor of health policy and clinical practice at Dartmouth University’s Geisel School of Medicine, stresses that the public needs to know whether the benefits outweigh the harms.
Woloshin cita Muir GrayBritish doctor and renowned public health expert, who stated: “all screening programs are bad; some also do well and, of these, some do more good than harm at a reasonable cost.”
Ultimately, evaluating the clinical utility of MCEDs could . Therefore, these tests may still be a long way from widespread use.
If this is the case, it is important that anyone considering using them takes into account both the potential benefit of early detection such as the potential harm associated with possible overdiagnosis, false positives and a yet-to-be-proven ability to save lives.
