Editorial review of meta-analysis investigating the link between ovarian cancer and oral contraceptive use (no authors listed); meta-analysis by Valerie Beral, MD, et al, published in The Lancet (2008;371:303–314). Methods
Meta-analysis of 45 epidemiological studies included 23,257 women who had ovarian cancer and 87,303 who did not, conducted in the 1960s, 1970s, and 1980s
Researchers adjusted for 15 factors that might play a role in whether a woman developed ovarian cancer
Results
Overall ovarian cancer risk in users of oral contraceptives (OCPs) was reduced
Protection conferred by OCPs seemed to start within a year of taking the pills and increase over time
Use for 15y or more lowered a woman's risk of ovarian cancer by 58%; Use for 10 to 14y cut risk by 44%; 5 to 9y of use cut risk by 36%; Even use for only 1 to 4y reduced risk by 22%
OCPs reduced incidence of serous, clear cell, and endometrioid cancers to a similar degree but had no significant effect on mucinous ovarian cancers
Even though the amount of estrogen used in birth control pills lessened between 1960 and 1980, the researchers did not see a different level of risk reduction
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