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Length Of Oral Contraceptive Use Raises Cervical Cancer Risks

The longer oral contraceptives are used, the higher the risk women have of developing cervical cancer, but evidence is still lacking on how long the risk remains when they stop using the pill.

An international collaboration is now re-analysing original data which researchers hope will provide more reliable estimates of how long the risk remains, explain Dr Valerie Beral and colleagues at Cancer Research UK at the University of Oxford, and the International Agency for Research on Cancer, Lyon, France.

The researchers point out that persistent infection of cervical epithelial cells with certain high-risk types of the human papillomavirus (HPV) is believed to be the most important cause of cervical cancer. It seems a high proportion of sexually-active women, at some time, are infected by one or more HPV viruses. Recent studies suggest there is an increased risk of cervical cancer in HPV-DNA positive women if they use oral contraceptives for longer than five years.

Data from 28 published studies, which included over 12,531 women with cervical cancer, were reviewed. The relative risk of cervical cancer increased with increasing duration of oral contraceptive use. At 5 years or less, the relative risk was 1.1, for 5 to 9 years, use the risk was 1.6, and for 10 or more years, the risk was 2.2 for all of the women. Among the women who were HPV positive the risks were 0.9, 1.3, and 2.5 respectively.

"The results were broadly similar for invasive and in situ cervical cancers, for squamous cell and adenocarcinoma, and in studies that adjusted for HPV status, number of sexual partners, cervical screening, smoking, or use of barrier contraceptives," the researchers declared.

Dr Beral and colleagues conclude that the limited published data suggest that the relative risk of cervical cancer associated with oral contraceptive might decline when pill use stops, but that could not be clearly deduced because study design varied. The upcoming collaborative reanalysis "should provide much needed reliable information on the effects of duration of use within categories of time since last use."
Lancet 2003;361:1159-67.

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