Abstract
PURPOSE:
Evidence
suggests that breast-feeding may decrease the risk of epithelial ovarian
cancer but it is not clear whether there is a relationship with
duration of breast-feeding, patterns of breast-feeding, or particular
histological subtypes of ovarian cancer. We sought to investigate these
issues in detail.
METHODS:
Data from participants in a
population-based study of ovarian cancer in western Washington State,
USA (2002-2007) who had had at least one birth (881 cases and 1,345
controls) were used to assess relations between patterns of
breast-feeding and ovarian cancer. Logistic regression was used to
calculate odds ratios (OR) and 95% confidence intervals (CI).
RESULTS:
Women
who ever breast-fed had a 22 % reduction in risk of ovarian cancer
compared with those who never breast-fed (OR = 0.78, 95% CI 0.64-0.96)
and risk reduction appeared greater with longer durations of feeding per
child breast-fed (OR = 0.56, 95% CI 0.32-0.98 for 18 months average
duration breast-feeding versus none). Introduction of supplementary
feeds did not substantially alter these effects. The overall risk
reduction appeared greatest for the endometrioid and clear cell subtypes
(OR per month of average breast-feeding per child breast-fed = 0.944,
95% CI 0.903-0.987).
CONCLUSIONS:
Among women who have
had the opportunity to breast-feed, ever breast-feeding and increasing
durations of episodes of breast-feeding for each breast-fed child are
associated with a decrease in the risk of ovarian cancer independent of
numbers of births, which may be strongest for the endometrioid subtype.
