Study links contraceptive pill with cervical cancer
Reported November 10, 2007
Scientists think the link between the contraceptive pill and an increased risk of cervical cancer is a biological effect of the hormones in the pill. (AFP)
A new study has confirmed that women who take the contraceptive pill are more at risk of developing cervical cancer later in life.
It has taken five years for British researchers to collate and analyse the data of more than 50,000 women in 26 countries. Their report has been published in the most recent Lancet medical journal.
What they found was that long-term use of the contraceptive pill can double a woman’s risk of developing cervical cancer.
Dr Jane Green from the Cancer Epidemiology Unit at Oxford University says the good news is that the risk goes away after a 10-year break from the pill.
“Ten years for it to disappear altogether,” she said.
“It starts to fall straight away, so even by two or three years you’ve got a substantial reduction in the actual risk, and by five and 10, it’s a linear fall.”
Dr Green says the exact link between the pill and cervical cancer is still unknown.
“In terms of pill use, we actually don’t know yet what the effect is, but we think that it is a biological effect – in other words, it’s not just that women who take the pill are more likely to get the HPV (human papillomavirus) infections, that’s not true.”
“So we think it is actually a biological effect of the hormones of the pill while you’re taking it, but we don’t know how it works.”
The researchers stress that the main cause of cervical cancer is the human papillomavirus, for which many women are now getting a vaccine.
Professor Robert Tindle is from the Clinical Medical Virology Centre at the University of Queensland.
“You must realise that oral contraceptives don’t cause cervical cancer,” he said.
“I mean, what causes cervical cancer in 99 per cent of cases is infection with human papillomavirus, and infection with certain types of human papillomavirus.
“Now, what this study shows is that those who have used oral contraceptives, particularly in their younger years, will be more prone to developing cervical carcinoma than those women who haven’t used oral contraceptives.”
He says many women contract this virus without ever developing cancer.
Small risk
Dr Green warns this study should not scare women off the pill, as the overall risk is small.
“If you take 1,000 women who don’t use the pill at all, by the age of 50, out of those 1,000 women 3.8 would have developed cervical cancer in total by the age of 50,” she said.
“And if you took 1,000 women who have used the pill for 10 years, between the ages of 20 and 30, then that number would increase to 4.5 per 1,000 women.
“So that’s 0.7 per 1,000 less than one extra case per 1,000 women by the age of 50 for 10 years’ use of the pill. So it [the risk] is small.”
Dr Green says the pill reduces the risk of developing other cancers, such as ovarian or cancer of the womb, which are much more difficult to detect than cervical cancer, often picked up early in regular pap smears.
Professor Robert Tindle says regular check-ups further reduce the risk.
“In many ways, much of the danger of oral contraceptives is circumvented by regular monitoring of the uterine cervix for early changes in the epithelium there, which is a forerunner of the disease,” he said.