Prevention & Risk
Stopping cancer from starting: vaccines, germline testing, lifestyle, and preventive drugs or surgery.
HPV and HBV vaccination, hereditary cancer syndrome testing (BRCA, Lynch), chemoprevention (tamoxifen, aspirin in Lynch), risk-reducing surgery, and population-level tobacco and alcohol control. The most cost-effective section of oncology and the least glamorous.
Alcohol causes at least seven cancers and there is no safe threshold. Price, availability and cancer warning labels are the tools that work; most people still do not know alcohol causes cancer.
Daily low-dose aspirin lowers bowel cancer risk in people with Lynch syndrome and appears to cut recurrence in bowel cancers with a particular mutation. In healthy older people it caused more harm than good.
People with severe obesity who have weight-loss surgery develop about a third fewer cancers over the following decade, especially womb and other hormone-related cancers, than similar people who do not.
Vaccinating people who do not have cancer yet but are very likely to get it, against the antigens their future tumour will carry.
The public systems that count every cancer diagnosis and death in a country, which tell us whether incidence and survival are improving.
Drugs or surgery for people at high inherited risk, before any cancer appears.
Coffee does not cause cancer and is probably protective against liver and womb cancer. Very hot drinks of any kind may raise oesophageal cancer risk.
Structured exercise during and after treatment, which the CHALLENGE trial showed improves survival in colon cancer.
A test of the DNA you were born with, to find inherited risk genes such as BRCA or Lynch syndrome.
Seventy percent of cancer deaths occur in low- and middle-income countries, where radiotherapy machines, pathologists, essential medicines and palliative care are scarce. Global oncology works on affordable, adapted care and the systems to deliver it.
GLP-1 agonists, the new weight-loss injections, lower weight by 15-20%. Early observational data suggest fewer obesity-related cancers in people who take them, but no trial has yet tested cancer as an outcome.
Vaccines that prevent the viral infections behind cervical, throat, anal, and liver cancers. The most effective anti-cancer intervention ever created.
Diets built around vegetables, wholegrains, legumes, nuts, fish and olive oil, with little red or processed meat, are linked with lower cancer risk and better survival after diagnosis. The evidence is strong for the pattern, weak for any single food.
Processed meat (bacon, ham, sausages) definitely causes bowel cancer; red meat probably does. The risk per person is modest, but because so many people eat it, the population impact is large.
Removing the fallopian tubes, where most ovarian cancer starts, during other pelvic surgery or in women at inherited risk.
Stopping smoking after a cancer diagnosis improves survival, reduces treatment complications and second cancers, and is the single most effective supportive intervention that oncology services still routinely fail to deliver.
For years women with breast cancer were told to avoid soy because it contains plant oestrogens. Large studies show moderate soy food intake is safe and may slightly reduce recurrence, including on tamoxifen.
Testing cheap old drugs, aspirin, metformin, statins, beta-blockers, as cancer treatments, because they are safe, available and sometimes work.
Destroying precancerous cervical cells with a heated or frozen probe in under a minute, the tool that makes screen-and-treat possible where there are no surgeons.
Time-restricted eating means eating within a window of 8-12 hours a day and fasting overnight. It improves blood sugar and weight a little; whether it changes cancer risk or recurrence is unknown.
Giving the innate immune system a memory, so monocytes and NK cells respond harder the next time they meet a tumour.
Diets high in industrially processed foods and sugary drinks are linked with more cancer, mainly through obesity but perhaps also through additives and packaging chemicals. Sugar itself does not 'feed' a tumour in the way social media claims.
The largest trial of vitamin D and fish-oil pills found they did not prevent cancer. A possible reduction in cancer deaths, and hints of benefit after a digestive cancer diagnosis, keep the question alive.
There is no safe level of alcohol for cancer risk, and the risk is highest for cancers of the mouth, throat, oesophagus, liver, bowel and breast. Public awareness is low; most people do not know alcohol causes breast cancer. Warning labels and minimum pricing are the policy levers being debated.
School-based vaccination at 12-13 with high uptake nearly abolishes cervical cancer in vaccinated cohorts, even with a vaccine covering only two HPV types. Screening intervals and the future of cervical screening can now be redesigned around vaccination status.
People with Lynch syndrome should be offered daily aspirin, which roughly halves bowel cancer risk with a delayed and durable effect. Whether a lower dose (as tested in CAPP3) is as effective, and whether the finding extends to the general population, are separate questions.
Because Lynch syndrome tumours make the same abnormal proteins in almost every patient, a single vaccine could in principle be given to carriers before cancer develops. This small trial showed the concept is safe and immunogenic; whether it prevents cancer requires the randomised trials now being planned.
Vaccinating girls before they are exposed to HPV prevents most cervical cancers. Catch-up vaccination in young adults still helps, but less. Combined with HPV screening, elimination of cervical cancer as a public health problem is a realistic goal.
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.
Maintaining a healthy weight is now established cancer prevention for over a dozen cancer types. For clinicians and policymakers, obesity belongs alongside tobacco and alcohol in prevention strategy. Whether intentional weight loss in adulthood reverses risk is still being studied, including in trials of GLP-1 drugs.
For women at raised risk, a 5-year course of tamoxifen offers long-lasting protection against the commonest kind of breast cancer. Uptake is low because of side effects and fear of rare serious harms; low-dose tamoxifen (TAM-01) is now being tested to improve the balance. It has not been shown to save lives.
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.
A Mediterranean dietary pattern rich in olive oil may lower breast cancer risk, and it is safe and good for the heart anyway. The evidence is suggestive, not definitive, because of the small number of cancers; it should not be presented as proven cancer prevention.
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.
For women who carry a BRCA mutation, preventive removal of the ovaries and tubes saves lives, and preventive mastectomy almost eliminates breast cancer. These are the strongest prevention effects in oncology, which is why finding carriers before they develop cancer matters so much.
Smoking is the single largest preventable cause of cancer death, and quitting at any age helps, with the greatest gain from quitting young. Cessation support belongs in every cancer service, including lung screening programmes.
Doll and Hill's 1950 study is where the evidence that smoking causes cancer begins. Everything from cigarette warnings and tax to smoke-free laws and lung screening eligibility descends from this study and the cohort that followed it.