Screening for breast, colorectal and cervical cancer — population, tests, performance and guidelines

Breast cancer — target population and guidelines. Women aged 40–74 (USPSTF 2024), biennial mammography; the American Cancer Society advises annual screening from 45 and biennial from 55, continuing while life expectancy exceeds 10 years. High-risk women (BRCA carriers, chest irradiation) start earlier with annual MRI plus mammography. In India, the ICMR and national programme (NPCDCS) recommend clinical breast examination every 3 years from age 30 because population mammography is not feasible — a crucial contextual point.

Breast cancer — tests and performance. Mammography: sensitivity approximately 75–85% (falling to 60– 70% in dense breasts, but rising with age as breasts become fattier), specificity 90–95%. Digital breast tomosynthesis improves cancer detection and reduces recall. Clinical breast examination: sensitivity about 50– 60%. Ultrasound is adjunctive for dense breasts; MRI has the highest sensitivity (over 90%) but lower specificity and is reserved for high risk.

Colorectal cancer — target population and guidelines. Average-risk adults aged 45–75 (USPSTF 2021); individualise between 76 and 85 years according to health status and prior screening, and do not screen beyond 85. Earlier and more intensive surveillance for a family history, Lynch syndrome, FAP or inflammatory bowel disease.

Colorectal cancer — tests and performance. FIT (faecal immunochemical test) annually — sensitivity about 75–80% for cancer but low (about 25%) for advanced adenoma, specificity about 95%; it is the most practical test for population screening in India. Multitarget stool DNA-FIT every 3 years — sensitivity about 92% for cancer, specificity about 87%. Colonoscopy every 10 years — the gold standard, sensitivity over 95%, but carries risks of perforation and bleeding that rise with age and sedation risk. CT colonography every 5 years; flexible sigmoidoscopy every 5 years. Any positive non-colonoscopic test must be followed by colonoscopy.

Cervical cancer — target population and guidelines. Women aged 21–65. Cytology alone every 3 years from 21–29; from 30–65, primary HPV testing every 5 years (preferred), co-testing every 5 years, or cytology every 3 years. Stop at 65 if there has been adequate prior negative screening (three consecutive negative cytology or two negative HPV tests in the preceding 10 years). Continue screening in older women who have never been screened — a large group in India, where cervical cancer remains a leading cause of cancer death. WHO recommends HPV DNA testing as the primary screening method from age 30, twice in a lifetime, in low-resource settings, alongside HPV vaccination.

Cervical cancer — tests and performance. Conventional Pap smear: sensitivity only about 50–60%, specificity over 95% — its programme effectiveness came from repetition, not single-test accuracy. Liquid-based cytology has similar sensitivity with fewer unsatisfactory samples. HPV DNA testing: sensitivity about 90– 95% with lower specificity (about 85–90%) — hence a longer screening interval and the need for triage of positives by cytology or genotyping. Visual inspection with acetic acid (VIA): sensitivity about 60–70%, specificity about 85% — cheap, single-visit, and the basis of India's national "see-and-treat" programme.

Self-collection for HPV testing and blood-based colorectal screening. The FDA has approved self-collected vaginal samples for primary HPV screening (2024), which markedly improves uptake among women who avoid pelvic examination — directly relevant to older and rural Indian women and now endorsed by WHO. For colorectal cancer, blood-based cell-free DNA testing (Shield, approved 2024) detects cancer with about 83% sensitivity but only about 13% sensitivity for advanced adenoma, so it is positioned as an option only for those who decline all other screening, not as an equivalent alternative to FIT or colonoscopy. Cross-reference: The principles governing whether an older person should be screened at all are given in Question 39.