Oral contraceptive use is associated with prostate cancer: an ecologic study

INTRODUCTION: Recently there have been several studies suggesting that estrogen exposure may increase the risk of prostate cancer (PCa). In this report we examine associations between PCa incidence and mortality and population-based use of oral contraceptives (OC's). We hypothesized that OC's by-products may cause an environmental contamination leading to an increased low level estrogen exposure and therefore higher PCa incidence and mortality. METHODS: The hypothesis was studied in an ecologic study. We used data from the “international agency for research on cancer” (IACR) to retrieve age-standardized rates of prostate cancer in 2007 and the “United Nations 2007 use of contraceptive report” to retrieve data on contraceptive use. We subsequently used a Pearson correlation and a multivariable linear regression to associate the percentage of women using OC's, intrauterine devices, condoms or vaginal barriers to the age standardized prostate cancer incidence and mortality. We performed these analyses by individual nation and by continent worldwide. RESULTS: OC's use was significantly associated with prostate cancer incidence and mortality in the individual nation world wide (r=0.61 and r=0.53, respectively p<0.05 for all). PCa incidence was also associated with OC's use in Europe (r=0.545 p<0.05) and by continent (r=0.522 p<0.05). All other forms of contraceptives (i.e. intra-uterine devices, condoms or vaginal barriers) were not correlated with prostate cancer incidence or mortality. On multivariable analysis the correlation with OC was independent of nation’s wealth. CONCLUSION: In this hypothesis generating ecologic study we have demonstrated a significant association between OC's and PCa. We hypothesize that oral contraceptive effect may be mediated through environmental estrogen levels; this novel concept is worth further investigation.