Indications and rationale for cancer screening in the elderly

Principles of screening (Wilson and Jungner). Screening is justified when the condition is an important health problem with a recognisable latent or early symptomatic stage, the natural history is understood, there is an acceptable, safe, sensitive and specific test, an accepted and effective treatment exists, facilities for diagnosis and treatment are available, and the process is continuous and cost-effective.

The rationale for screening older adults. Cancer is fundamentally a disease of ageing — incidence and mortality both peak in old age, and over 60% of cancers occur in those above 65 — so the absolute benefit of detecting a screen-detectable cancer is greatest in this group. Older people have historically been under-screened and under-treated, presenting at later stage with poorer outcomes.

The counter-argument — why screening can harm the old. There is a lag time to benefit of approximately 10 years for mammography and colonoscopy and about 5 years for FIT: harms (bleeding, perforation, anxiety, false positives) are immediate while benefits are delayed. Additional harms are overdiagnosis of indolent tumours that would never have caused symptoms (especially prostate and breast), lead-time and length-time bias creating an illusion of benefit, and the burden of investigating false positives in frail patients.

The decisive rule — life expectancy, not chronological age. Screening should be offered when estimated life expectancy exceeds the lag time to benefit — in practice, more than 10 years. Estimate life expectancy from comorbidity, function and validated tools (ePrognosis, Lee index, Charlson comorbidity index), not from the birth date. A fit 80-year-old woman may have 10 years of life expectancy and benefit; a frail 68-year-old with heart failure and dementia will not.

Practical age limits in current guidance. Breast — biennial mammography to age 74 (individualised beyond). Colorectal — screen 45–75; individualise 76–85 based on health and prior screening; do not screen after 85. Cervical — stop at 65 if there has been adequate prior negative screening (but continue if never screened, which is common among older Indian women). Prostate — shared decision-making between 55 and 69; do not screen routinely above 70. Lung — annual low-dose CT for ages 50–80 with a ≥20 pack-year history who currently smoke or quit within 15 years.

How to decide and communicate. Use shared decision-making — present absolute benefit and harm in natural frequencies, elicit the patient's values and goals of care, and consider whether the patient would accept the investigation and treatment that a positive result would demand. If they would decline colonoscopy or surgery, the screening test should not be done. Deprescribing screening ("stopping screening") should be framed positively as a shift towards care that helps now, rather than as withdrawal of care, and documented. In the Indian context, screening should also be balanced against limited resources and the very low baseline coverage — opportunistic screening at the point of care is often more realistic than organised programmes.

USPSTF 2024 breast cancer screening statement (JAMA 2024;331:1918) — now recommends biennial mammography for all women aged 40 to 74 (Grade B), lowering the starting age from 50, while concluding that evidence remains insufficient for screening women aged 75 and older (Grade I). This crystallises the geriatric teaching point: the upper limit of screening is not defined by a trial but by individual life expectancy and shared decision-making, which is why the answer must always pivot to functional status rather than age. Cross-reference: The individual screening programmes, tests and their sensitivity and specificity are tabulated in Question 40.