Breastfeeding may reduce risk for ovarian cancer
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Breastfeeding appeared to be associated with reduced risk for overall ovarian cancer and for the high-grade serous subtype, according to results of a pooled analysis published in JAMA Oncology.
The results suggest breastfeeding is a potentially modifiable factor that could lower risk for ovarian cancer separate from pregnancy alone, researchers noted.
“Ovarian cancer survival remains poor, with 5-year survival less than 50%, mostly owing to late detection,” Ana Babic, PhD, instructor in medicine at Harvard Medical School and Dana-Farber Cancer Institute, and colleagues wrote. “Prevention is crucial for reducing mortality from this disease. With few modifiable risk factors beyond oral contraceptive use, identifying additional modifiable factors is needed to tailor prevention strategies.”
Previous studies have shown breastfeeding reduces risk for epithelial ovarian cancer, whereas other research showed no correlation. Additionally, associations between duration and timing of breastfeeding and reduced ovarian cancer risk appeared inconsistent, and it remained unclear whether any reduction in risk conferred by breastfeeding augments that of pregnancy alone.
Babic and colleagues conducted a pooled analysis of 9,973 parous women (mean age, 57.4 years; standard deviation [SD], 11.1) with ovarian cancer and 13,843 controls (mean age, 56.4 years; SD, 11.7) from 13 Ovarian Cancer Association Consortium case-control studies to determine the association between breastfeeding and risk for ovarian cancer overall and by histotype.
The studies included data collected from individual sites between November 1989 and December 2009. Women reported breastfeeding history — including duration per child breastfed, age at first and last breastfeeding, and years since last breastfeeding — through interviews and questionnaires.
Researchers used multivariable logistic regression to calculate ORs and 95% CIs for the overall association, and polytomous logistic regression to estimate histotype-specific associations.
Diagnosis of epithelial ovarian cancer served as the main outcome of the study.
Results showed breastfeeding was associated with a 24% lower risk for invasive ovarian cancer (OR = 0.76; 95% CI, 0.71-0.8).
Regardless of parity, ever having breastfed appeared associated with reduced risk for all invasive ovarian cancers, especially high-grade serous and endometrioid cancers.
Among invasive tumors, researchers reported statistically significant associations between breastfeeding and decreased risk for high-grade serous (OR = 0.75; 95% CI, 0.7-0.81), endometrioid (OR = 0.73; 95% CI, 0.64-0.84) and clear cell tumors (OR = 0.78; 95% CI, 0.64-0.96).
The investigators also identified associations between longer duration of breastfeeding and reduced risk for invasive ovarian cancer compared with women who never breastfed. Mean breastfeeding duration of 1 to 3 months appeared associated with an 18% lower risk (OR = 0.82; 95% CI, 0.76-0.88), whereas breastfeeding for 12 or more months appeared associated with a 34% lower risk (OR = 0.66; 95% CI, 0.58-0.75).
Results also showed associations between more recent breastfeeding and reduction in risk (OR = 0.56; 95% CI, 0.47-0.66 for less than 10 years), and that risk reduction persisted for decades (OR = 0.83; 95% CI, 0.77-0.9 for 30 years or greater).
“Breastfeeding is associated with a significant decrease in ovarian cancer risk overall and for high-grade serous tumors, the most lethal subtype,” Babic and colleagues wrote. “[WHO] recommends exclusive breastfeeding for at least 6 months and continued breastfeeding with complementary foods for 2 or more years. Our results support these recommendations, while noting that breastfeeding fewer than 3 months per child is still associated with significant ovarian cancer risk reduction.” – by John DeRosier
Disclosures: Babic reports research funding from NIH. Please see the study for all other authors’ relevant financial disclosures.
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