Journal of the National Cancer Institute Advance Access published online on April 29, 2008
JNCI Journal of the National Cancer Institute, doi:10.1093/jnci/djn099
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© The Author 2008. Published by Oxford University Press.
ARTICLES |
Screening-Preventable Cervical Cancer Risks: Evidence From a Nationwide Audit in Sweden
Affiliations of authors: Department of Obstetrics and Gynecology, Gävle Hospital, Gävle, Sweden (BA); Cancer Screening Unit, Oncologic Center M8, Karolinska University Hospital, Stockholm, Sweden (LK, ST); Department of Medical Epidemiology and Biostatistics, Karolinska Institutet, Stockholm, Sweden (PS); Department of Obstetrics and Gynecology, Umeå University Hospital, Umeå, Sweden (LS); Oncologic center, Western Region, Sahlgrenska University Hospital, Göteborg, Sweden (BS); Department of Pathology and Clinical Cytology, Sahlgrenska University Hospital, Göteborg, Sweden (WR); Department of Medical Microbiology, Lund University, University Hospital, Malmö, Sweden (JD)
Correspondence to: Bengt Andrae, MD, Department of Obstetrics and Gynecology, Gävle Hospital, S-801 87 Gävle, Sweden (e-mail: bengt.andrae{at}gmail.com).
Background: The effectiveness of cervical cancer screening programs differs widely in different populations. The reasons for these differences are unclear. Routine and comprehensive audits have been proposed as an ethically required component of screening. We performed a nationwide audit of the effectiveness of the Swedish cervical cancer screening program.
Methods: We identified all invasive cervical cancer cases that were diagnosed in Sweden from January 1, 1999, through December 31, 2001, and had been reported to the Swedish Cancer Registry (n = 1230 cases). We verified the diagnoses by histopathologic rereview and matched each case subject to five (population-based) age-matched control subjects who were identified from the National Population Register. The Pap smear screening histories for case and control subjects were reviewed for a 6-year period using the National Cervical Cancer Screening Register, which contains data on essentially all relevant cytological and histological diagnoses in Sweden. Odds ratios (ORs), and their 95% confidence intervals (CIs), of cervical cancer according to screening history were calculated in conditional logistic regression models. All statistical tests were two-sided.
Results: Women who had not had a Pap smear within the recommended screening interval had higher risk of cervical cancer than women who had been screened (OR = 2.52, 95% CI = 2.19 to 2.91). This risk was similarly increased for all age groups (Phomogeneity = .96). The risk for nonsquamous cell cervical cancers (OR = 1.59, 95% CI = 1.20 to 2.11) was also increased. Women who had not had a Pap smear within the recommended screening interval had a particularly high risk of advanced cancers (OR = 4.82, 95% CI = 3.61 to 6.44). Among women who had been screened within the recommended interval, those with abnormal Pap smears had a higher risk of cervical cancer than those with normal smears (OR = 7.55, 95% CI = 5.88 to 9.69) and constituted 11.5% of all women with cervical cancer.
Conclusions: Nonadherence to screening intervals was the major reason for cervical cancer morbidity. The screening program was equally effective for women of all ages and was also effective against nonsquamous cancers.
| CONTEXT AND CAVEATS Prior knowledge The effectiveness of cervical cancer screening programs differs widely in different populations, but the reasons are unclear. Routine and comprehensive audits have been proposed as an ethically required component of screening. Study design A comprehensive nationwide audit of the effectiveness of the organized cervical cancer screening program in Sweden. Contribution Not having had a Pap smear taken within the recommended screening interval was the most important risk factor for cervical cancer in the presence of a screening program. The screening program was equally effective for women of all ages, including women younger than 30, and was also effective against nonsquamous cancers. Implications Compliance with screening recommendations and high population coverage of screening are vital for success. Limitations Attendance to the screening program (ie, the relationship between invitations issued and tests performed) was not studied because only some counties kept identifiable information on when and to whom invitations had been issued.
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Manuscript received August 20, 2007; revised February 15, 2008; accepted March 4, 2008.
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J Natl Cancer Inst 2008 100: 605-606.
J Natl Cancer Inst 2008 100: 603.
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