Study finds trend toward grade III breast tumors in women who breast-feed longer-- Beth Gilbert
Friday, March 26, 2010 (Last Updated: 03/29/2010)
FRIDAY, March 26 (HealthDay News) -- A longer duration of breast-feeding may be associated with unfavorable breast tumor characteristics, according to a study presented at the European Breast Cancer Conference, held from March 24 to 27 in Barcelona, Spain.
Salma Butt, M.D., of the Malmö University Hospital in Sweden, and colleagues followed 17,035 women in The Malmö Diet and Cancer Study until December 31, 2004. Overall, 622 incident breast cancers were diagnosed during follow-up. The researchers evaluated these cancers along with duration of breast-feeding, which was categorized in four quartiles (<2.2 months, 2.2 to <4.0 months, 4.0 to <6.2 months, and ≥6.2 months per child).
They found that the overall risk of breast cancer was similar in all the quartiles of mean duration of breast-feeding. In women with a higher mean time of breast-feeding, there was a statistically significant trend toward grade III tumors. An increasing mean time of breast-feeding was significantly associated with risk of high Ki67 expressing tumors. While there was a trend toward tumors with high cyclin D1 and low P27 with longer breast-feeding durations, these associations were not statistically significant. In addition, longer mean duration of breast-feeding was associated with estrogen receptor-negative tumors, but this association was also not statistically significant.
"We conclude that long duration of breast-feeding was associated with more unfavorable breast tumor characteristics," the authors write.
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