Does screening history explain the ethnic differences in stage at diagnosis of cervical cancer in New Zealand?

Abstract

Background: There are ethnic disparities in cervical cancer survival in New Zealand. The objectives of this study were to assess the associations of screening history, ethnicity, socio-economic status (SES) and rural residence with stage at diagnosis in women diagnosed with cervical cancer in New Zealand during 1994-2005. Methods: The 2323 cases were categorized as 'ever screened' if they had had at least one smear prior to 6 months before diagnosis, and as 'regular screening' if they had had no more than 36 months between any two smears in the period 6-114 months before diagnosis. Logistic regression was used to estimate the associations of screening history, ethnicity, SES and urban/rural residence with stage at diagnosis. Results: The percentages 'ever screened' were 43.3% overall, 24.8% in Pacific, 30.5% in Asian, 40.6% in Māori and 46.1% in 'Other' women. The corresponding estimates for 'regular screening' were 14.0, 5.7, 7.8, 12.5 and 15.3%. Women with 'regular screening' had a lower risk of late stage diagnosis [odds ratio (OR) 0.16, 95% confidence interval (CI) 0.10-0.26], and the effect was greater for squamous cell carcinoma (OR 0.12, 95% CI 0.07-0.23) than for adenocarcinoma (OR 0.32, 95% CI 0.13-0.82). The increased risk of latestage diagnosis (OR 2.72, 95% CI 1.99-3.72) in Māori (compared with 'Other') women decreased only slightly when adjusted for screening history (OR 2.45, 95% CI 1.77-3.39). Conclusions: Over half of cases had not been 'ever screened'. Regular screening substantially lowered the risk of being diagnosed at a late stage. However, screening history does not appear to explain the ethnic differences in stage at diagnosis. © The Author 2009; all rights reserved. Published by Oxford University Press on behalf of the International Epidemiological Association.