LONDON (Reuters Health) - Long-term use of oral contraceptives increases the risk of cancer of the cervix up to fourfold in women infected with the human papillomavirus (HPV), according to study findings released by The Lancet on Tuesday.

HPV is a common sexually transmitted infection that often goes away on its own. But infection with certain HPV strains is linked to an increased risk of cervical cancer.

Researchers at the World Health Organisation's International Agency for Research on Cancer pooled data from 10 studies involving patients with cervical cancer and healthy "control" patients. The journal lifted its normal publication embargo after reports of the study results appeared in British newspapers.

The analysis of eight case-control studies included 1,676 women with cancer and 255 controls, all of whom were infected with HPV. Results were adjusted for education, indicators of sexual activity and screening history as well as age and geographic location.

The investigators found no increased risk of cervical cancer in women who had used oral contraceptives for less than 5 years compared with women who had never taken oral contraceptives.

But women who had taken the Pill for 5 to 9 years were nearly three times more likely to develop cervical cancer, while those who used oral contraceptives for 10 years or longer had a more than fourfold increased cancer risk, Dr. Victor Moreno from the Catalan Institute for Oncology in Barcelona, Spain, and colleagues report.

"Long-term use of oral contraceptives could be a cofactor that increases the risk of cervical carcinoma by up to fourfold in women who are positive for cervical HPV DNA," they state.

Timothy Farley, of the department of reproductive health and research at the World Health Organisation (WHO) in Geneva, said the new research helped clarify the different risks involved in cervical cancer.

"We've known for some time that women who take the Pill have a greater risk of developing cervical cancer. We haven't been sure if it's the effect of the Pill or the effect of people's behaviour. Women who have a high number of sexual partners have a high risk of cancer," he told Reuters Health.

"We don't know for sure if it is behavioural or not but that seems less likely than before. It may be an effect of the Pill," he said.

"Our results could help women who have persistent HPV infection to balance benefits--such as prevention of pregnancy and cancers of the ovary--and harms of long-term oral contraceptive use, and suggest that long-term users of oral contraceptives should be included in cervical screening programmes."

Farley noted, "It is very important to realise that the risk of developing cervical cancer is very small. The majority of women who develop cervical cancer have never even seen (an oral contraceptive pill). There is no reason for women to change the use of the Pill because of the results of this study."

He added, "People should not decide against using the Pill because of concerns about cervical cancer. It's a risk, but a small risk. The benefits of the Pill in terms of quality of life and preventing unwanted pregnancies far outweigh that risk."

SOURCE: The Lancet online 2002 March 27.

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