Key Facts

Screening aims to detect cancer or pre-cancer at an early stage when treatment is more effective. Screening programmes must demonstrate net benefit at a population level.

Epidemiology

• Breast screening prevents approximately 1,300 deaths per year in England
• Cervical screening prevents approximately 5,000 cancers and 5,000 deaths per year
• Bowel cancer screening reduces CRC mortality by approximately 15-20%
• Overall screening uptake in England: breast ~71%, cervical ~72%, bowel ~65%

Aetiology

Screening programmes target cancers with:

• High incidence and mortality
• Recognisable pre-clinical phase
• Effective treatment for early-stage disease
• An acceptable and feasible test

Pathophysiology

• Breast: mammography detects small cancers and DCIS before clinical presentation
• Cervical: HPV testing detects persistent HPV infection; cytology triage identifies CIN
• Bowel: FIT detects haemoglobin in stool from polyps or cancers
• Lung: low-dose CT detects early-stage lung cancer in high-risk smokers/ex-smokers

Screening Pathways

• Breast: invitation letter → mammography at screening unit → results within 2 weeks → recall for further assessment if abnormal (5% recall rate)
• Cervical: invitation letter → sample by practice nurse/GP → HPV test → cytology triage if HPV+ → colposcopy if abnormal
• Bowel: FIT kit posted home → collect stool sample → return by post → results within 2 weeks → colonoscopy if positive (≥10mcg Hb/g faeces)

Abnormal Results Management

• Each programme has defined pathways for investigation and treatment
• Patient support and counselling are integral

Red Flags

• Symptoms between screening rounds must be investigated promptly ("interval cancers")
• A normal screening result does not exclude cancer
• Patients with symptoms should not wait for scheduled screening

Bedside

• Screening test as per programme (mammogram, cervical sample, FIT)

Bloods

• Not part of current UK screening programmes
• PSA screening: not recommended as a population programme (debate ongoing)

Imaging

• Mammography: 2-view (CC + MLO) digital mammography
• LDCT: for lung cancer screening (high-risk populations)

Special Tests

• FIT: quantitative measurement of haemoglobin in faeces; threshold ≥10mcg Hb/g for colonoscopy referral
• HPV testing: detects high-risk HPV DNA from cervical sample
• Colonoscopy: diagnostic investigation after positive FIT
• Colposcopy: diagnostic investigation after abnormal cervical screening

Non-pharmacological

• Public health campaigns to improve uptake
• Address barriers: language, accessibility, anxiety, cultural factors
• Informed consent: ensure understanding of benefits and harms
• Quality assurance programmes for each screening service

Pharmacological

• Not directly part of screening
• HPV vaccination: primary prevention complements cervical screening
• Chemoprevention: aspirin for CRC prevention (not yet part of screening programme)

Surgical/Interventional

• Treatment of screen-detected abnormalities as per cancer-specific guidelines
• Polypectomy at colonoscopy for bowel adenomas
• LLETZ for high-grade CIN
• Surgery/chemotherapy for screen-detected cancers

Referral Criteria

• Abnormal screening results: defined referral pathways within each programme
• Symptomatic patients: do not delay for screening; investigate via 2-week wait pathway
• High-risk individuals: may qualify for enhanced/earlier screening (e.g. breast MRI for BRCA carriers)

• Breast screening: reduces breast cancer mortality by ~20% in screened population
• Cervical screening: prevents ~70% of cervical cancer deaths
• Bowel screening: reduces CRC mortality by ~15-20%
• Lung cancer screening (NELSON trial): 24% reduction in lung cancer mortality with LDCT
• Overdiagnosis rates: breast screening ~11-19%; cervical CIN1 ~60% regress; bowel polyps — not all progress
• Screen-detected cancers generally have better stage distribution and outcomes than symptomatic cancers

NHS Cancer Screening Programmes Summary

Wilson and Jungner Screening Criteria