A claim you hear on longevity podcasts
Mixed. Of 10 studies that test it, 4 partly agree, 4 disagree and 2 agree.
The claim checked: Blood tests for many cancers, used on everyone, are unlikely to cut cancer deaths and bring false alarms Hear it at 6:56
Two of ten studies agree. The NHS-Galleri trial tested adults aged 50 to 77 in England: late-stage cancers were no less common in the tested group. Four disagree, but all four are computer models, not tests on real people. One projects 17 to 21% fewer cancer deaths. Two of the models were paid for by the test's maker. Four are mixed. A review found no results yet on deaths, and no trial here has reported them.
Computed from 10 studies that test this point, each judged by two readers, in full. 10 more studies are waiting for a full read and do not count yet.
“at least for now, we know that if you just take those tests and unloosen them on a general population. So, without selecting for high-risk people, without selecting for people who have had cancer before um we know that those tests are probably not going to work.”
controlled trial · 2026
“Stage III/IV cancer incidence rate did not differ significantly between intervention and control arms (IRR: 1.03 [0.92-1.14], p=0.63).”
Effect of Screening with Multicancer Early-Detection Test on Late-Stage Cancer Diagnosis. N Engl J Med
Who: Adults aged 50-77 in 8 English Cancer Alliance regions with no cancer diagnosis or treatment in the prior 3 years and not under investigation for cancer (NHS-Galleri RCT)
PMID 42776074
other primary study · 2021
“Grail’s current and previous clinical trial data, including those reported recently [ 25 ], do not warrant population screening based on analysis of methylation patterns, even if such tests are highly specific.”
Can Circulating Tumor DNA Support a Successful Screening Test for Early Cancer Detection? The Grail Paradigm. Diagnostics (Basel)
Who: No new participants; a perspective/review using published empirical data and the authors' own calculations on ctDNA amounts versus tumor size, plus Grail's case-control validation data
PMID 34943407
systematic review · 2025 · landmark
“No meaningful results were reported relating to patient-relevant outcomes, such as mortality, potential harms, HRQoL, acceptability or satisfaction.”
Multi-cancer early detection tests for general population screening: a systematic literature review. Health Technol Assess
Who: Studies of blood-based MCED tests; target population individuals aged 50-79 without clinical suspicion of cancer
PMID 39898371
other primary study · 2025
“The model estimated that the NHS-Galleri trial could reduce late-stage incidence by 6% to 23% over 3 years and cancer mortality by 6% to 9% for the targeted cancers over 5 years.”
Clinical Significance of a Multicancer Screening Trial With Stage-Based End Points. JAMA Netw Open
Who: Simulated NHS-Galleri trial population in England (median age 66) using NCRAS incidence, stage and survival data for 50-79-year-olds diagnosed 2013-2018, for 11 cancer types
PMID 41066125
controlled trial · 2026
“The primary endpoint of the NHS-Galleri trial—reduction in the incidence rate of stage III/IV cancers in the intervention arm versus the control arm—was not met and is reported elsewhere 26 .”
Performance of a multi-cancer early detection test in the randomized controlled NHS-Galleri trial. Nat Med
Who: Adults aged 50-77 at invitation in eight NHS Cancer Alliance regions of England, randomized to annual Galleri MCED testing plus usual care or usual care (blood stored)
PMID 42773209
trial or observed group · 2025
“Given the strong link between earlier‐stage diagnosis and improved survival, it is likely that MCED testing will result in survival gains, though this remains to be demonstrated in long‐term, real‐world studies.”
The impact of multicancer early detection tests on cancer stage shift: A 10-year microsimulation model. Cancer
Who: Simulated closed cohort of US adults aged 50 to 84 years (born 1931-1965) without a cancer diagnosis, matched to the 2015 US population by sex, race and age; 14 solid tumor cancer types (microsimulation model, no real participants)
PMID 41208393
other primary study · 2023
“The reduction in five-year cancer mortality was between 1787 and 2257 per 100,000 persons in the screening programme (between 17 and 21%) in the fast dwell time scenario with HR = 3 and slow dwell time scenario with HR = 1, respectively.”
Modelled mortality benefits of multi-cancer early detection screening in England. Br J Cancer
Who: Modelled population of 50-79-year-olds in England using NCRAS cancer incidence and survival data for cancers diagnosed 2013-2018
PMID 37185463
other primary study · 2024
“Table 4 shows that the relative reduction of cancer-specific mortality reached 13%–16% for all dwell time scenarios at year 5 for three rounds of annual MCED screening, and 16%–19% at year 7 for five rounds of annual MCED screening.”
Clinical performance and utility: A microsimulation model to inform the design of screening trials for a multi-cancer early detection test. J Med Screen
Who: Simulated US population aged 50-79 based on SEER cancer incidence, stage and survival data (2006-2015), with a 15% healthy volunteer reduction
PMID 38304990
other primary study · 2025
“However, both annual and biennial MCED screening intervals have the potential to avert deaths associated with late-stage cancers when used in addition to current guideline-based cancer screening.”
Assessment of the impact of multi-cancer early detection test screening intervals on late-stage cancer at diagnosis and mortality using a state-transition model. BMJ Open
Who: Modelled US population aged 50-79 using SEER18 incidence and cancer-specific survival (diagnosed 2006-2015, followed to 2018)
PMID 40341158
other primary study · 2022
“Screening with an MCED test in addition to usual care for multiple types of cancer can lead to earlier cancer detection, which may improve patient survival and lower treatment costs.”
The Potential Value-Based Price of a Multi-Cancer Early Detection Genomic Blood Test to Complement Current Single Cancer Screening in the USA. Pharmacoeconomics
Who: Simulated (modeled) cohort of US adults aged 50-79 not previously diagnosed with cancer; no people were studied
PMID 36038710
Seven of ten studies agree. In women aged 65 to 75, 1.0% had a PET-CT scan after a false alarm and 0.22% had an invasive test for nothing. In a large US and Canadian study, 46.3% of people with a false alarm had invasive procedures. Three are mixed. In the NHS-Galleri trial in England, the false-alarm rate was 0.45%, lower than for some single-cancer screening tests.
Computed from 10 studies that test this point, each judged by two readers, in full. 3 more studies are waiting for a full read and do not count yet.
other primary study · 2020 · landmark
“1.0% of participants underwent PET-CT imaging based on false positive blood tests, and 0.22% underwent a futile invasive diagnostic procedure.”
Feasibility of blood testing combined with PET-CT to screen for cancer and guide intervention. Science
Who: Women aged 65-75 with no personal history of cancer enrolled through the Geisinger Health System (DETECT-A)
PMID 32345712
other primary study · 2023 · landmark
“Most had both laboratory tests (26/33, 79% TP; 50/57, 88% FP) and imaging (30/33, 91% TP; 53/57, 93% FP).”
Blood-based tests for multicancer early detection (PATHFINDER): a prospective cohort study. Lancet
Who: Convenience sample of adults aged 50 or older without signs or symptoms of cancer at seven US health networks; 56% had additional risk (smoking, genetic predisposition or prior cancer)
PMID 37805216
other primary study · 2025
“Imaging tests were performed at a similar rate of 90% for both true positives (90.5%, 19/21) and false positives (88.9%, 16/18; Table 2 ), whereas approximately two times more true positives than false positives underwent nonsurgical and/or surgical procedures [true positives: nonsurgical 76.2% (16/21) and surgical 14.3% (3/21); false positives: nonsurgical 38.9% (7/18) and surgical 0% (0/18); Table 2 ].”
Clinical Evaluation of Cancer Signal Origin Prediction and Diagnostic Resolution following Multicancer Early Detection Testing in the PATHFINDER Study. Cancer Prev Res (Phila)
Who: PATHFINDER participants (adults aged 50 or older without clinical suspicion of cancer) who tested positive on both the initial and refined MCED test versions and had a workup
PMID 40265568
trial or observed group · 2026
“Almost twice as many participants with true-positive versus false-positive MCED test results (88.6% versus 46.3%) had invasive procedures during targeted evaluation (Fig. 2a and Supplementary Table 5 ).”
Performance and safety of a multi-cancer early detection test: the PATHFINDER 2 study. Nat Med
Who: Adults aged 50 or older at 32 US and Canadian sites without clinical suspicion of cancer and no cancer diagnosis or treatment in the prior 3 years (PATHFINDER 2)
PMID 42773207
systematic review · 2025 · landmark
“No adverse events were reported for either test; however, for the earlier version of the GRAIL MCED test, time to diagnostic resolution was shorter for those with a TP result compared to a FP result and over 90% of participants with FP results required further imaging tests.”
Multi-cancer early detection tests for general population screening: a systematic literature review. Health Technol Assess
Who: Studies of blood-based MCED tests; target population individuals aged 50-79 without clinical suspicion of cancer
PMID 39898371
trial or observed group · 2025 · landmark
“We recorded 26 false positive cases, including eight cases (0.09%, Table 2 ) with precancerous lesions in the colon and 18 cases (0.20%, Table 2 ) with diagnostic results unable to confirm the presence of malignant or precancerous tumors.”
Prospective validation study: a non-invasive circulating tumor DNA-based assay for simultaneous early detection of multiple cancers in asymptomatic adults. BMC Med
Who: Asymptomatic adults aged 40 or older with no cancer history at 75 hospitals and one research institute in Vietnam (K-DETEK); 42% classed high risk
PMID 39948555
other primary study · 2024
“Among the 98 participants with FP CancerSEEK results, cancer was ruled out by 18-F-FDG PET-CT alone in 63 cases, while 35 participants had further noninvasive or minimally invasive procedures to rule out cancer or to investigate the 18-F-FDG PET-CT findings.”
Outcomes Following a False-Positive Multi-Cancer Early Detection Test: Results from DETECT-A, the First Large, Prospective, Interventional MCED Study. Cancer Prev Res (Phila)
Who: Women aged 65-75 with no personal history of cancer in DETECT-A (Geisinger Health System); this analysis follows the 98 with a false-positive CancerSEEK result
PMID 38705577
other primary study · 2025
“Diagnostic evaluation for 4 patients with MCD-positive signals did not reveal a source of the signal.”
Implementation of a Multicancer Detection (MCD) Test in a Tertiary Referral Center in Asymptomatic Patients: An 18-Month Prospective Cohort Study. J Prim Care Community Health
Who: Asymptomatic patients in a Mayo Clinic general internal medicine executive health practice; 21% had a prior cancer diagnosis
PMID 40132152
other primary study · 2026
“To achieve diagnostic resolution, true positive cases required a median of three diagnostic tests or procedures (range, 2–7), whereas false positives required a median of five tests (range, 4–6).”
Diagnostic Outcomes among Patients with Positive Multi-Cancer Early Detection Test Results. Cancer Res Commun
Who: Adults with a prior positive Galleri result who presented to the Dana-Farber Cancer Institute MCED clinic (mostly self-referred, tests from employers, insurers or the company website)
PMID 41721625
controlled trial · 2026
“The aggregate false-positive rate (0.45%) for the MCED test was also below what has been reported for single-cancer screening tests, which range from 0.98% to 19.9% 32 – 35 .”
Performance of a multi-cancer early detection test in the randomized controlled NHS-Galleri trial. Nat Med
Who: Intervention-arm participants aged 50-77 in England (NHS-Galleri) with evaluable MCED results traced in the national cancer registry
PMID 42773209
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