Breastfeeding and Ovarian Cancer
by Anne Eglash MD, IBCLC, FABM
According to the authors of this week’s article ‘Ovarian cancer in the world: epidemiology and risk factors’, ovarian cancer is the 7th most common cancer among women and accounted for 4.4% of all cancer-related mortality among women world-wide in 2018. It has the highest risk of death among all gynecologic cancers, and is 3 times more lethal than breast cancer. Although ovarian cancer rates are highest among non-hispanic whites, the mortality rate for individuals with ovarian cancer are highest among African populations due to healthcare inequality.
The authors sought to review the world-wide literature on the incidence and risk factors of ovarian cancer. They identified 145 studies fitting their criteria for this systematic review. The greatest risk of ovarian cancer is family history of breast or ovarian cancer, or personal history of breast cancer. More than 20% of ovarian cancers are due to gene mutations. They found that incessant ovulation increases the risk of ovarian cancer. This means that factors contributing to lack of ovulation, such as pregnancy, lactation and birth control, reduce the risk of ovarian cancer. The greater the number of pregnancies, the lower the risk of ovarian cancer. The age at menarche or menopause is not related to the risk of ovarian cancer.
- The longer a mother breastfeeds, the lower her risk of ovarian cancer.
- The greater the number of breastfed children, the lower her risk of ovarian cancer.
- The risk of ovarian cancer decreases by 44% for 18 months average duration of breastfeeding (vs no breastfeeding).
- Ever breastfeeding is associated with a 22% reduced risk of ovarian cancer.
See the Answer
Ovarian cancer is one of the most common gynecologic cancers that has the highest mortality rate. Considering the fact that knowledge on the incidence, mortality of ovarian cancer, as well as its risk factors is necessary for planning and preventing complications, this study was conducted with the aim of examining the epidemiology and risk factors of ovarian cancer in the world.
Materials and Methods
In order to access the articles, Medline, Web of Science Core Collection, and Scopus databases were searched from their start to the year 2018. Full-text, English observational studies that referred to various aspects of ovarian cancer were included in the study.
In total, 125 articles that had been published during the years 1925–2018 were entered into the study. Ovarian cancer is the seventh most common cancer among women. Increased risk factors of cancer have led to an upward trend in the incidence of cancer around the world. In 2018, 4.4% of entire cancer-related mortality among women was attributed to ovarian cancer. Although the incidence of cancer is higher among high Human Development Index (HDI) countries, the trend of mortality rate tends to be reversing. Various factors affect the occurrence of ovarian cancer, from which genetic factor are among the most important ones. Pregnancy, lactation, and oral contraceptive pills play a role in reducing the risk of this disease.
This study provides significant evidence about ovarian cancer. Considering the heavy burden of ovarian cancer on women's health, preventive measures as well as health education and early detection in high risk groups of women are highly recommended. Although some risk factors cannot be changed, a focus on preventable risk factors may reduce the risk of ovarian cancer. More studies are needed to explore the role of unclear risk factors in ovarian cancer occurrence.
This systematic review has a useful chart summarizing the various factors that protect women from ovarian cancer, or conversely increase the risk. They identified only 4 factors that protect, including lactation, parity, higher age at childbirth, and contraceptive methods. The article does point out that the #1 risk factor for ovarian cancer is a genetic mutation, such as BRCA1 or BRCA2. A case-control study published in 2015 found that breastfeeding for more than 12 months was associated with a 38% and 50% reduction in risk of ovarian cancer among BRCA1 and BRCA2 mutation carriers, respectively. So, even for women who are at high risk of ovarian cancer due to genetics, breastfeeding is protective. I hope that this fact is shared by genetic counselors when advising women who test positive for those genetic mutations that increase the risk of breast and/or ovarian cancer.