Screening and cervical cancer cure: population based cohort studyBMJ 2012; 344 doi: https://doi.org/10.1136/bmj.e900 (Published 01 March 2012) Cite this as: BMJ 2012;344:e900
- Bengt Andrae, senior consultant12,
- Therese M-L Andersson, doctoral student2,
- Paul C Lambert, reader23,
- Levent Kemetli, statistician4,
- Lena Silfverdal, senior consultant5,
- Björn Strander, senior consultant6,
- Walter Ryd, associate professor7,
- Joakim Dillner, professor28,
- Sven Törnberg, associate professor4,
- Pär Sparén, professor2
- 1Centre for Research and Development, Uppsala University/County Council of Gävleborg S-80188 Gävle, Sweden
- 2Department of Medical Epidemiology and Biostatistics, Karolinska Institutet, Stockholm, Sweden
- 3Department of Health Sciences, Centre for Biostatistics and Genetic Epidemiology, University of Leicester, Leicester, UK
- 4Department of Cancer Screening, Karolinska University Hospital, Stockholm, Sweden
- 5Department of Obstetrics and Gynaecology, Umeå University Hospital, Umeå, Sweden
- 6Department of Obstetrics and Gynaecology, Institute of Clinical Sciences, Sahlgrenska Academy, Gothenburg University, Sweden
- 7Department of Pathology and Clinical Cytology, Sahlgrenska University Hospital, Gothenburg, Sweden
- 8Department of Laboratory Medicine, Karolinska Institutet, Stockholm, Sweden
- Correspondence to: B Andrae
- Accepted 8 December 2011
Objective To determine whether detection of invasive cervical cancer by screening results in better prognosis or merely increases the lead time until death.
Design Nationwide population based cohort study.
Participants All 1230 women with cervical cancer diagnosed during 1999-2001 in Sweden prospectively followed up for an average of 8.5 years.
Main outcome measures Cure proportions and five year relative survival ratios, stratified by screening history, mode of detection, age, histopathological type, and FIGO (International Federation of Gynecology and Obstetrics) stage.
Results In the screening ages, the cure proportion for women with screen detected invasive cancer was 92% (95% confidence interval 75% to 98%) and for symptomatic women was 66% (62% to 70%), a statistically significant difference in cure of 26% (16% to 36%). Among symptomatic women, the cure proportion was significantly higher for those who had been screened according to recommendations (interval cancers) than among those overdue for screening: difference in cure 14% (95% confidence interval 6% to 23%). Cure proportions were similar for all histopathological types except small cell carcinomas and were closely related to FIGO stage. A significantly higher cure proportion for screen detected cancers remained after adjustment for stage at diagnosis (difference 15%, 7% to 22%).
Conclusions Screening is associated with improved cure of cervical cancer. Confounding cannot be ruled out, but the effect was not attributable to lead time bias and was larger than what is reflected by down-staging. Evaluations of screening programmes should consider the assessment of cure proportions.
Contributors: BA, PS, ST, JD, and BS conceived the audit. BA, PS, TM-LA, PCL, and JD conceived this analysis. BA, LS, LK, ST, and PS collected and standardised the audit database. WR reviewed the diagnostic histopathology specimens of all cancer cases. TM-LA, PCL, and PS did the statistical analyses and drafted the statistical methods section. BA drafted the manuscript with PS and JD. All authors actively participated in the discussion and approved the final version. PS is guarantor.
Funding: This work was supported by grants from the Swedish Cancer Society (02-6988 and 2010/900), the Swedish Foundation for Strategic Research (KF 10-0046), Gävle Cancer Fund (2009-09-17), and the Centre for Research and Development, Uppsala University/County Council of Gävleborg, Sweden (CFUG-82261). The corresponding author had full access to all the data in the study and had the full responsibility to submit the report for publication. The study was conducted and analysed independently from its funders.
Competing interests: All authors have completed the ICMJE uniform disclosure form at www.icmje.org/coi_disclosure.pdf (available on request from the corresponding author) and declare: no support from any organisation for the submitted work; no financial relationships with any organisations that might have an interest in the submitted work in the previous three years; and no other relationships or activities that could appear to have influenced the submitted work.
Ethical approval: This study was approved by the ethical review boards in Uppsala, Stockholm, Umeå, Gothenburg, and Lund and the joint board of Örebro and Linköping, Sweden (FEK Ups 01-322 and EPN 2008/185). The ethical review boards determined that informed consent from participating women was not required.
Data sharing: The analysis dataset for this study is available from the corresponding author at.
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