ORAL-CONTRACEPTIVES AND CERVICAL-CANCER - FURTHER FINDINGS FROM THE OXFORD FAMILY-PLANNING ASSOCIATION CONTRACEPTIVE STUDY

In 1983, we reported results from the Oxford Family Planning Associati on contraceptive study regarding the association between oral contrace ptives (OCs) and cervical neoplasia, after a 10 year follow-up of a co hort of 17000 women. Further findings from this study are reported her e after an additional 12 years of follow-up. A nested case-control des ign was used in which cases were all women diagnosed under 45 years of age with invasive carcinoma (n=33), carcinoma in situ (n=121) or dysp lasia (n=159). Controls were randomly selected from among cohort membe rs and matched to cases on exact year of birth and clinic attended at recruitment to study. Conditional logistic regression analysis was use d to determine odds ratios (ORs) and 95% confidence intervals (CIs) as sociated with various aspects of OC use relative to never users adjust ed for social class, smoking, age at first birth and ever use of diaph ragm or condom. Ever users of OCs had a slightly elevated OR for all t ypes of cervical neoplasia combined (OR=1.40, 95% CI 1.00-1.96). Odds ratios were highest for invasive carcinoma (OR=4.44, 95% CI 1.04-31.6) , intermediate for carcinoma in situ (OR=1.73, 95% CI 1.00-3.00) and l owest for dysplasia (OR=1.07, 95% CI 0.69-1.66). The elevated risk ass ociated with OC use appeared to be largely confined to current or rece nt (last use in the past 2 years) long-term users of OCs. Among curren t or recent users, ORs for all types of cervical neoplasia combined we re 3.34 (95% CI 1.96-5.67) for 49-72 months of use, 1.69 (95% CI 0.97- 2.95) for 73-96 months and 2.04 (95% CI 1.34-3.11) for 97 or more mont hs. These results suggest a possible effect of OC use on later stages of cervical carcinogenesis, although residual confounding due to sexua l factors or human papillomavirus (HPV) infection cannot be ruled out.