Early Detection & Screening
Early detection and screening means finding cancer before it causes symptoms, when it is most curable.
Population screening (mammography, colonoscopy, low-dose CT, HPV testing, PSA) has proven mortality benefit in several cancers. Blood-based multi-cancer early detection (MCED) and risk-adapted AI screening aim to extend this to cancers with no screening today.
Smelling cancer: measuring the trace chemicals a tumour puts into exhaled breath.
Fragmentomics reads the sizes and positions of DNA fragments in blood, not the mutations. Cancer cells die messily and leave a recognisable fragmentation pattern.
Finding and removing polyps before they become cancer. Colonoscopy prevents cancer; stool and blood tests catch it early and get more people screened.
Looking at the cervix with a magnifier after a positive screen, then removing the abnormal patch with an electric wire loop in a clinic visit.
Magnified skin imaging and whole-body photo mapping, increasingly read by algorithms, to find melanoma early and avoid unnecessary biopsies.
Reading chemical tags on DNA that reveal a cell's identity, used to classify brain tumours and to detect cancer in blood.
Removing very early cancers of the oesophagus or stomach from the inside with an endoscope, so the organ is kept intact.
People with cirrhosis or chronic hepatitis B get a liver ultrasound and a blood test every six months so cancer is caught while it is still curable.
Yearly MRI or endoscopic ultrasound for people with inherited risk, which catches pancreatic cancers while they are still operable.
A swab tested for the virus that causes cervical cancer, more accurate than the Pap smear and doable at home.
A yearly low-radiation CT scan for current and former heavy smokers that finds lung cancer early enough to cure it.
Low-dose breast X-ray used for screening. Newer 3D versions find more cancers with fewer false alarms.
Reads a mammogram to estimate five-year breast cancer risk, consistently across races and devices.
A single blood test intended to screen for dozens of cancers at once, including ones with no screening today.
Predicts a person's six-year lung cancer risk from one low-dose CT, even when no nodule is visible.
Scanners sensitive enough to image the whole body in seconds at a fraction of the radiation dose, which raises the question of whether healthy people should be scanned at all.
Whole-body MRI is an MRI of the entire body without radiation, used to find spread in myeloma and to screen people with high inherited cancer risk.
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.
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.