Pill Use Appears Likely To Increase Risk of Some Forms of Cervical Cancer

Abstract

Two recent case-control studies suggest that the risk of cervical cancer may be increased by oral contraceptive (OC) use. The first involving 195 women from Los Angeles California who had been diagnosed with adenocarcinoma of the cervix in 1977-91 and 386 matched controls found that ever-use of OCs doubled the risk of cervical cancer (odds ratio 2.1). The risk was highest (4.4) among women who had used OCs for more than 12 years. Once duration of OC use was controlled there was no additional cancer risk associated with age at initiation of OC use duration of OC use before 20 years of age or before first pregnancy time since first or last OC use type of pill taken and frequency of Pap smears. The second study involving 2168 women recruited from a colposcopy clinic in Quebec Canada in 1988-89 identified 548 women with at least one late-stage cervical intraepithelial neoplasia (CIN) and 338 women with early-stage CIN. 612 women with no signs of neoplasia cervical cancer or human papillomavirus (HPV) served as controls. Ever-users of OCs had a 40% increased risk of late-stage CIN compared with never-users. Women who had used OCs for six or more years were almost twice as likely (relative risk 1.9) to have late-stage CIN while those who had used OCs for less than two years were at no elevated risk (0.9). The risk of early-stage CIN was not affected by OC use regardless of duration. Late-stage CIN was also strongly associated with smoking (relative risks of 2.4 among current and 1.3 among former smokers). Risks of both early and late-stage CIN were at least doubled among women with four or more lifetime sexual partners. Most significant however was the association with past HPV infection; these women were 8.7 times as likely as those not infected to have late-stage CIN. It remains unclear whether smoking and OC use affect initiation of late-stage CIN in the absence of HPV or whether they accelerate the progression of early-stage CIN or subclinical HPV to late-stage lesions.