Cancer Screening

Cancer screening applies tests that can find a cancer before it causes symptoms, or find changes that can be removed before they turn into cancer. Bowel screening uses a stool test for hidden blood or a colonoscopy, which can also remove polyps on the spot. Breast screening uses mammography, often as 3D tomosynthesis, with ultrasound or MRI added for dense breasts or a high inherited risk. Cervical screening uses a sample from the cervix tested for the human papillomavirus, HPV, and for abnormal cells. Lung screening uses a low-dose CT scan for people with a heavy smoking history. Prostate screening relies on the PSA blood test, followed by MRI when the value is raised. A skin examination looks for suspicious moles. These tests do not diagnose cancer on their own: an abnormal result leads to further tests, such as a biopsy, to confirm or exclude it.

Screening is offered by age and risk. For people at average risk, bowel screening usually starts at about 45 to 50, breast screening between about 40 and 50, and cervical screening in the mid-twenties, continuing at set intervals. A yearly low-dose lung CT is recommended for heavy current or recent former smokers, generally from about 50. Men from about 50 can discuss the PSA test with a doctor and decide together, because its benefit is balanced against the risk of finding cancers that need no treatment. Skin checks suit people with many moles, fair skin with past sunburn or a previous skin cancer. A strong family history, a known gene change such as BRCA or Lynch syndrome, inflammatory bowel disease or previous radiotherapy to the chest means earlier and more frequent screening, often with different tests, planned by a specialist. Tumour marker blood tests are not recommended as screening for people at average risk.

The visit usually starts with a consultation in which a physician reviews your age, history and family history and confirms which tests suit you. Blood samples are taken, including PSA for men who have chosen it. Mammography compresses each breast briefly between two plates for a few seconds per image, and an ultrasound may follow. The cervical sample is taken during a short gynaecological examination with a speculum, much like a routine smear. A low-dose lung CT takes only a breath-hold. A skin check examines the whole body, sometimes with a dermatoscope or mole mapping photographs. Colonoscopy is usually scheduled separately: after a day of bowel preparation at home or in the hotel, a flexible camera examines the large bowel under sedation in about 20 to 40 minutes, and polyps are removed during the same procedure. At the end, a physician reviews the available results and explains the next steps.

Screening is for people without symptoms; anyone with a lump, bleeding, a change in bowel habit, unexplained weight loss or a persistent cough should have a diagnostic assessment instead. Before booking, write down which relatives had cancer, which type and at what age, and bring any genetic test results and previous screening reports, so intervals and tests can be set correctly. Colonoscopy needs a low-fibre diet for a day or two and a bowel-cleansing drink the evening before and on the morning of the test; blood thinners and diabetes medicines may need adjusting on medical advice. Cervical tests are more reliable away from your period, avoiding intercourse and vaginal products for about two days. On the mammography day, avoid deodorant or powder under the arms. Tell the team about any pregnancy, implants or previous breast surgery. Arrange for someone to accompany you after sedation.

Most screening tests need no recovery and you can return to normal activities straight away. After a sedated colonoscopy you may feel bloated for a few hours; rest for the rest of the day, do not drive or sign important documents, and have someone with you. Flying is usually fine the next day, although if a large polyp was removed your doctor may advise waiting a little longer because of the small risk of delayed bleeding. A practical plan is to arrive a day early, start bowel preparation if a colonoscopy is included, and allow two to three days in total. Results of biopsies, polyp analysis and cervical tests usually take about 1 to 2 weeks and are sent electronically, with remote discussion. Ask for written reports and images, and agree when each test should be repeated, so your doctor at home can keep the programme on schedule.

Screening tests are generally safe, but each has limits. Colonoscopy carries small risks of bleeding and, rarely, perforation of the bowel, as well as risks from sedation. CT and mammography use low doses of radiation, which is one reason they are offered at set intervals rather than repeatedly. False positives are common across screening programmes: a mammogram, lung scan or PSA test can raise an alarm that turns out to be nothing after further imaging or a biopsy, causing worry and extra procedures. Overdiagnosis is the detection of slow cancers, especially in the prostate, breast and thyroid, that would never have caused symptoms but are then treated. False negatives also occur, so a normal result does not exclude cancer, and new symptoms must still be reported. Used selectively and repeated at the right intervals, screening reduces deaths from bowel, breast, cervical and lung cancer.