With the vast increase in the use of the contraceptive pill over the past 40 years, the amount of oestrogen entering the water supply may be partly responsible for the increased incidence of prostate cancer around the world, Canadian researchers speculate.
Excess oestrogen is known to cause various cancers, and the widespread use of the pill might raise environmental levels of the hormone.
"Recent studies have shown that oestrogen exposure may increase the risk of prostate cancer," said lead researcher Dr David Margel, a clinical fellow in the Department of Surgical Oncology at Princess Margaret Hospital and the University of Toronto.
"We wanted to explore whether there was an association with a woman's use of oral contraceptives to prostate cancer incidence or mortality," he explained. Although the amounts of oestrogen excreted by a woman is minimal, when millions of women do it over a long period of time, it might cause a low-level environmental contamination, Margel said.
The report is published online in the edition of BMJ Open.
For the study, Margel and his colleague Dr. Neil E. Fleshner, researchers at the university's Health Network, used data from the International Agency for Research on Cancer and the United Nations World Contraceptive Use report to identify the rates of prostate cancer and prostate cancer deaths, as well as the proportion of women using contraceptive pills.
Margel and Fleshner complied data on countries and continents around the world to see if there was any connection between contraceptive pills and prostate cancer.
The researchers looked at some 100 countries and found that where the use of oral contraceptives was high, so was the rate of prostate cancer. These findings did not change based on a nation's wealth, they added.
"It seems as if the European countries had the highest association," Margel said.
The use of other contraceptives such as intrauterine devices, condoms or other vaginal barriers was not associated with an increased risk of prostate cancer.
"I want to stress this is a hypothesis-generating study," Margel said. "In no way do we prove cause-and-effect."
Most common male cancer
To further explore the connection, the researchers are planning to test water and look for oestrogen levels in patients with prostate cancer.
Prostate cancer is the most common male cancer in the developed world, and the use of the contraceptive pill is widespread, the researchers noted.
Prostate cancer expert Dr Anthony D'Amico, chief of radiation oncology at Brigham and Women's Hospital in Boston, said that "it's hard to know if this is true.
This is a study of association, not cause-and-effect. Even the hypothesis it's based on is questionable."
D'Amico noted that even if there is oestrogen from contraceptives in drinking water or food, a person would have to drink the water and somebody would then have to measure the amount of oestrogen in the blood.
But even then, most compounds the body takes in are not absorbed, he added.
In fact, for a man to get micrograms of oestrogen into the blood, he would have to ingest milligrams of oestrogen. "You would have to have a lot in the water to believe this," D'Amico said.
D'Amico also said that small amounts of oestrogen raise the risk for a heart attack. "If you have enough to cause prostate cancer, you also have enough to cause a heart attack – so it's hard to accept."
Based on these speculative findings, "men should not be concerned," D'Amico said.
(HealthDay, Steven Reinberg, November 2011)
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