Effectiveness of cervical screening with age: population based case-control study of prospectively recorded dataBMJ 2009; 339 doi: http://dx.doi.org/10.1136/bmj.b2968 (Published 29 July 2009) Cite this as: BMJ 2009;339:b2968
- Peter Sasieni, professor of biostatistics and cancer epidemiology,
- Alejandra Castanon, epidemiologist,
- Jack Cuzick, John Snow professor of epidemiology
- 1Cancer Research UK Centre for Epidemiology, Mathematics and Statistics, Wolfson Institute of Preventive Medicine, Bart’s and The London School of Medicine, Queen Mary University of London, London EC1M 6BQ
- Correspondence to: P Sasieni
- Accepted 16 July 2009
Objective To study the effect of cervical screening on incidence of cervical cancer as a function of age with particular focus on women screened under the age of 25.
Design Population based case-control study with prospectively recorded data on cervical screening.
Setting Selected centres in the United Kingdom.
Participants 4012 women aged 20-69 with invasive cancer diagnosed in participating centres and two controls per case individually matched on age and area of residence.
Main outcome measures Odds ratios for strength of association between cervical cancer and screening at particular ages.
Results There is no evidence that screening women aged 22-24 reduced the incidence of cervical cancer at ages 25-29 (odds ratio 1.11, 95% confidence interval 0.83 to 1.50). Similar results were seen for cancers restricted to squamous carcinoma or FIGO (International Federation of Gynaecology and Obstetrics) stage IB or worse, but the numbers are insufficient to provide narrow confidence intervals. Screening was associated with a 60% reduction of cancers in women aged 40, increasing to 80% at age 64. Screening was particularly effective in preventing advanced stage cancers.
Conclusions Cervical screening in women aged 20-24 has little or no impact on rates of invasive cervical cancer up to age 30. Some uncertainly still exists regarding its impact on advanced stage tumours in women under age 30. By contrast, screening older women leads to a substantial reduction in incidence of and mortality from cervical cancer. These data should help policy makers balance the impact of screening on cancer rates against its harms, such as overtreatment of lesions with little invasive potential.
We thank all those who have helped with the design and conduct of this study and acknowledge the participation of millions of women and nameless healthcare professionals in the cervical screening programmes in the UK.
Working group members: Joanna Adams, Alejandra Castanon, Jack Cuzick, Elaine Farmery, Hillary Fielder, Muir Gray, David Mesher, Julietta Patnick, and Peter Sasieni.
Local collaborators: C Camilleri-Ferrante and A Thompson (East Anglia); P Grey and M J Platt (Macclesfield and Warrington); D Haran (Chester and Wirral); F Fowler (Southend); S Chatterton (Oxfordshire, Northants, Buckinghamshire, Berkshire); S Butterworth, M Vaille and J Underdown (Maidstone); R Swann (Medway); L Robinson (south west Surrey, west Surrey and north east Hampshire); A Burtenshaw (Mid Downs); S Samarsinghe (Kingston and Richmond); C Furlong (Enfield and Haringey); C Singleton (N Derbyshire); K Boyd (East Dorset); A Herbert and C Breen (Southampton and south west Hampshire); E Farmery (Wiltshire and Bath); L Daborn and K Jaber (west Dorset); J Grainger (Shropshire); G D H Thomas (Calderdale); W Young (Humberside); S Jennings (Leicestershire); F Boer (Brighton and Hove); R J Fitzmaurice (Huddersfield); Y Burlay and H Belza (Grimsby); S Barraclough and H Belza (Scunthorpe). I Duncan and K A Hussein (Dundee and Angus); L Reay (Argyll and Clyde); L Caughley (Northern Ireland); S Burgess (Clwyd); DC Watkins (Gwent); Helen Beer (Cervical Screening Wales); Quality Assurance Reference Centre (QARC) in north west England and the QARC in east England.
Contributors: PS participated in the design and establishment of the study, collation of data, design of the database, and analysis of the data. AC participated in the collation and analysis of the data. JC participated in the design and establishment of the study. All authors wrote the paper and saw and approved the final version. PS is guarantor.
Funding: This work was supported by Cancer Research UK (C8162/A6127 and C8162/A9481) and previously by the NHS cervical screening programme. Neither organisation had any input in the analysis or interpretation of the data or the writing of the paper.
Competing interests: None declared.
Ethical approval: Not required. Permission to link cervical screening and histology (cancer registration) data has been granted by the Patient Information Advisory Group (PIAG).
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