Most lethal cancers are found late
Screening exists for only a few cancers. Pancreatic, ovarian, liver, oesophageal and most lung cancers are found when cure is unlikely.
Stage at diagnosis is the largest single determinant of survival: localised pancreatic cancer has a five-year relative survival around 44% in SEER data, distant disease about 3%. Organised population screening exists only for breast, cervical and colorectal cancer, low-dose CT for heavy smokers, and prostate in some systems, and uptake is incomplete even where it exists. The cancers that kill most people at a late stage (pancreas, ovary, liver, oesophagus, stomach, most lung cancers in never-smokers) have no screening test, and the largest randomised trial of ovarian screening (UKCTOCS) found no mortality benefit despite a stage shift. Multi-cancer early detection blood tests (Galleri, Shield, fragmentomics) can detect signals from dozens of cancers but have modest sensitivity for stage I disease and have not yet shown reduced mortality; the NHS-Galleri trial is the first randomised test of the concept. Risk-stratified surveillance (new-onset diabetes for pancreas, cirrhosis for liver, Barrett's for oesophagus) is the intermediate strategy.
- Most lethal cancers arise in deep organs without symptoms until they are locally advanced or metastatic.
- Screening tests for low-prevalence cancers need very high specificity to avoid harm, which few biomarkers achieve.
- A stage shift does not guarantee a mortality reduction, so each test needs a long randomised trial that few sponsors fund.
- Screening uptake is incomplete and unequal even for tests that work, because of access, cost and awareness.
- Health systems lack the diagnostic capacity (imaging, endoscopy, pathology) to work up the positives a population test would generate.
- NHS-Galleri randomised about 140,000 people to GRAIL's multi-cancer blood test, the first trial of MCED on stage shift and mortality.
- The NCI Cancer Screening Research Network's Vanguard study is piloting MCED evaluation in the US.
- Guardant's Shield blood test was FDA-approved in 2024 for colorectal screening, and Exact Sciences' Cologuard has expanded stool DNA testing.
- The USPSTF broadened lung screening eligibility in 2021 and the NHS is rolling out targeted lung health checks nationally.
- Cirrhosis-based HCC surveillance and new-onset-diabetes pancreatic surveillance cohorts (NCI/NIDDK New-Onset Diabetes cohort) target high-risk groups.
- Delfi, Freenome and Harbinger are developing fragmentomic and methylation-based tests aimed at earlier-stage sensitivity.
A positive blood test with no known tumour is frightening and hard to manage. A standard imaging cascade with a time limit, and a registry of what was found, would make these tests usable.
Volatile compounds in breath differ in cancer. A breath test validated in truly symptomatic patients, not lab volunteers, could tell GPs who needs urgent scans and who can safely wait.
One in five cancers in the UK is first found in an emergency, usually late. Adding a cancer test to the blood already taken in A&E for over-60s with vague symptoms could catch some earlier.
Set a legal limit: anyone referred with suspected cancer should be told within 28 days whether they have it. Publish how every hospital performs each month.
You cannot manage what you do not measure quickly. Publishing stage at diagnosis by cancer and region every quarter, not years later, would show whether detection efforts are working.
People are invited separately for bowel, breast, cervical and lung screening and many miss some. One appointment offering all eligible tests, plus a risk assessment, would raise uptake.
A pill on a string collects cells from the food pipe and finds Barrett's oesophagus, a precursor of cancer. Offering it in pharmacies to people on long-term heartburn drugs would find it early.
Most cancer deaths are in low and middle income countries, where scans and endoscopies are scarce. A cheap methylation blood test tuned to liver, stomach, oesophageal, cervical and breast cancer could fill the gap.
Most people referred for blood in the urine do not have bladder cancer, yet all get cystoscopy. A urine DNA or methylation test could safely spare most of them.
Instead of separate screening programmes for a few cancers, assess every adult's overall cancer risk and offer blood tests, imaging and preventive treatment tuned to that risk, all inside one system that learns.
Most screening CT scans are normal. Letting a validated AI clear them, and sending only flagged scans to a radiologist, would let screening scale without more radiologists.
Pancreatic cancer is often visible in hindsight on earlier scans. Software trained on those pre-diagnostic scans could flag subtle changes while surgery is still possible.
To prove a leftover-cancer test works you need blood taken years before relapse. Collecting and freezing yearly samples now makes every future test testable.
Nasopharyngeal cancer is common in southern China and is caused by a virus. A blood test for viral DNA finds it early, and a large study showed better survival. Scale it up.
Computers can combine minor symptoms, blood tests and age into a cancer risk score in the background. Showing that score to the GP could get more people referred earlier.
How DNA fragments in blood are chopped up differs in cancer and can be read with cheap, shallow sequencing. Used as a first sieve, it could cut the cost of population screening.
Mouth cancer is common where tobacco is chewed and is visible to the naked eye. Health workers with a phone camera and AI could find it early in villages.
Hundreds of millions of CT scans are done each year for other reasons. Software could check each one for early lung, kidney, liver and pancreas changes, but only if a follow-up system exists.
Millions now wear continuous glucose monitors. A sudden, unexplained worsening of glucose control in a middle-aged wearer could be flagged as a possible early sign of pancreatic cancer.
Blood tests that look for many cancers at once take a decade to prove they save lives. Regulators could accept fewer late-stage cancers as the first answer, if trials keep counting deaths afterwards.
Pack-year rules miss many people who get lung cancer, including East Asian women who never smoked. A risk score with family history and ancestry would find more cancers per scan.
Dentists see the mouth more than any doctor. A standard, recorded oral cancer examination with a referral route would catch cancers earlier at almost no cost.
When a screening test misses a cancer, we should know. Linking every negative result to the cancer registry and publishing what was missed, by stage, should be a condition of use.
Vans equipped with ultrasound, biopsy kits, cervical screening and a link to a distant pathologist could bring a cancer diagnosis, and for cervical pre-cancer immediate treatment, to villages far from any hospital.
Screening finds cancers that would never have caused harm alongside dangerous ones. Pair every screening test with a test that says which is which, so people with harmless findings can safely watch and wait.
PSA screening finds too many harmless cancers. Using PSA plus a genetic risk score to select men, and MRI before any biopsy, finds the dangerous ones and skips the rest.
People with vague symptoms like fatigue and weight loss get many scans. A blood test could point to which organ to look at first, or safely reassure.
About one in a hundred people who develop diabetes after 50, more if they are losing weight, have pancreatic cancer. A simple score could send them for a scan or blood test.
Blood tests for bowel cancer miss most precancerous polyps, so they should not replace stool tests. But for the third of people who never do any screening, a blood test may beat nothing.
A woman with a breast lump should be examined, scanned and biopsied on the same day, and hear the result within a few days, rather than visiting four times over two months.
Whether finding cancer earlier saves lives depends on the cancer. Public models, one per cancer, would let trials and payers predict the mortality benefit from a stage shift honestly.
Bowel screening uses one blood-in-stool threshold for everyone. Setting it by age, sex and the person's previous results would find more cancers with the same number of colonoscopies.
A cancer blood test improves every year, but a ten-year trial tests the old version. Regulators and sponsors could agree in advance how updates are validated and carried into the result.
Current blood tests miss leftover cancer in many patients. Reading thousands of mutations at once, rather than a few dozen, can detect far smaller amounts.
Weight loss, fatigue and unexplained pain do not point to one organ, so patients bounce between specialists. A single clinic that investigates such symptoms quickly finds cancers that would otherwise be found late.
How long people wait between first noticing something wrong and being diagnosed is barely measured. Recording it routinely and publishing it by hospital would expose where the system loses time.
Randomise people through the national health system, post the blood kit, and read cancer deaths off the registry. That is ten times cheaper per participant than a classic trial.
People with cirrhosis are meant to have ultrasound scans twice a year, but most do not. A blood test done with their routine liver bloods could catch liver cancer earlier.
AI for screening should be judged on whether it finds dangerous cancers earlier and misses fewer, not just on whether it agrees with radiologists on old images.
Sweden's MASAI trial showed AI can safely replace one of two radiologists. Rolling it out region by region in a randomised order would prove it works at national scale and that interval cancers do not rise.
Instead of every woman every two or three years, an AI reading of the current mammogram would set who comes back in one year and who can safely wait four.
Losing weight without trying is one of the strongest signs of hidden cancer, but it is rarely measured. Automatic alerts from recorded weights could prompt a check-up.
People who grew up in East Asia, Eastern Europe or Latin America keep a high stomach cancer risk after migrating. Cheap blood tests could select who needs an endoscopy.
Survivors who had chest radiotherapy as young women, or certain chemotherapies, have much higher risks of specific second cancers. They should be screened like people with inherited risk, and today most are not.
People most at risk of lung cancer are least likely to attend hospital screening. Manchester showed mobile scanners in car parks reach them. Make this the default model.
Common gene variants shift a person's cancer risk several-fold. A one-time genetic score could tell each person when to start breast, bowel or prostate screening.
A platelet count that is normal but rising year on year, or haemoglobin drifting down, can signal cancer. Records already hold these trends; software could use them.
People with an inherited TP53 mutation face a near-certain lifetime cancer risk. Yearly whole-body MRI catches cancers early; adding blood DNA tests may catch them earlier still.
AI can take over one reader's work in double-reading screening programmes while finding more cancers. Whether the extra cancers found are ones that would have harmed women, and whether interval cancers fall, is the question the trial's primary endpoint will answer.
A multi-cancer blood test can be run in ordinary clinics, and most positive results can be resolved with imaging. But six in ten positives are false alarms that take months to resolve, and the test misses most cancers. Whether it reduces late-stage cancer or deaths is unknown; that requires randomised trials.
NHS-Galleri is the trial that will decide whether a blood test for many cancers at once should be offered by a health system. Its endpoint is a reduction in late-stage cancer rather than deaths, so even a positive result leaves the mortality question to be settled by longer follow-up.
A colonoscopy probably does reduce bowel cancer risk for the person who has it, but a programme that offers colonoscopy achieves much less if most people decline. Programmes based on stool tests with high uptake may deliver as much population benefit at lower cost and risk.
A blood test can find early, treatable cancers in people who feel well, including cancers for which no screening exists. It is not a replacement for mammography or colonoscopy but a possible addition. Larger randomised trials are needed to show benefit outweighs harm.
Lung screening works when it uses volumetric nodule management, and it works against a no-screening control. The protocol underpins the UK Targeted Lung Health Check programme and European recommendations. Benefit in women remains less precisely estimated.
Women can collect their own screening sample at home with no loss of accuracy if the laboratory uses a PCR test. Sending kits directly is the most effective way to reach women who do not attend, which matters because most cervical cancers occur in under-screened women.
Carrying a cancer mutation is normal; most mutant clones never become cancer. This means blood or tissue tests that look for driver mutations alone will produce false positives, and that the question of what tips a mutant clone into cancer (tissue environment, further hits, immune surveillance) is as important as the mutation itself.
Many older people carry blood clones one or two steps from leukaemia, and those clones also drive heart disease through inflammation. CHIP is why blood-based cancer tests must filter out mutations from blood cells, and it opens a route to preventing both leukaemia and cardiovascular events in carriers.
There are not thousands of cancer genes, and any one patient's tumour is driven by only a few of them. That makes targeted sequencing panels sensible, but because most drivers are lost tumour suppressors, drugs exist for only a minority, which is why the same group turned to early detection.
For people with a heavy smoking history, an annual low-dose CT scan is one of the few screening tests proven to reduce cancer deaths. Most abnormal scans are not cancer, so screening must be paired with careful nodule management. It does not apply to never-smokers or light smokers.
A cheap home stool test, repeated yearly or every two years and followed by colonoscopy when positive, prevents bowel cancer deaths. This is what national bowel screening programmes do today, with FIT replacing the older guaiac test.