Is There A Link Between the Pill and Prostate Cancer?

That’s a provocative question, which has been raised by a Canadian study reported in BMJ Open.  A search for an association between prostate cancer incidence and mortality and population-based use of contraceptives was instigated by suggestions that estrogen exposure may increase the incidence of this cancer.  The theory being tested in this study was that oral contraceptive by-products may cause contamination of the environment, i.e. an increased low level of estrogen exposure and thus more prostate cancer.  Data came from the International Agency for Research on Cancer on the rates of prostate cancer in 2007, from the United Nations World Contraceptive Use 2007 report, and the World Factbook to retrieve information on gross domestic product (GDP) per capita in each country.  The relevant data were for individual countries and continents. Standard statistical methods were used to examine possible correlations between the first two sets of data – prostate cancer and contraceptive use.

The analyses showed that oral contraceptive use was significantly (and strongly) linked with the incidence of prostate cancer in individual countries worldwide and by continent. Mortality from prostate cancer was also linked in this way, but was not shown for countries within Europe or by continent. The other forms of contraception – intra-uterine devices, condoms, and vaginal barriers - showed no such associations with prostate cancer.  And there was no influence of GDP on the associations shown.  

The investigators in this study say that their findings are ‘hypothesis generating’.  In other words, such associations are not evidence, but strongly suggest that a more conclusive study should be undertaken.  What can be learned from this study?  It seems possible (even probable) that breakdown products of oral contraceptives could be passed via the urine into the environment in general or the drinking water, thus exposing the population at large.  If this is indeed the case, it should be possible to measure such contamination.  And the consequences of positive findings may indeed be more serious than just an increase in prostate cancer (which is serious enough).