Analysis of data collected from over 8000 women with ovarian cancer has drawn new conclusions regarding risk factors in the four most common ovarian malignancies – serous, mucinous, endometrioid and clear cell tumors. The findings, presented yesterday at the National Cancer Research Institute Cancer Conference (1–4 November 2015, Liverpool, UK), indicate that number of children and tubal ligation lower the risk of different types of ovarian cancer to different levels.
Women with one child were determined to have a 20% reduction in risk of ovarian cancer overall, and a 40% lower risk of endometrioid and clear cell tumors. Following this, each additional birth was associated with an approximate 8% reduction in overall ovarian cancer risk.
The study also investigated the impact of tubal ligation on ovarian cancer risk. Women who had undergone this procedure also had a 20% reduction in risk of ovarian cancer overall. Specifically, risk was approximately 20% lower for high-grade serous tumors and approximately 50% lower for endometrioid and clear cell tumors.
“In the last few years, our understanding of ovarian cancer has been revolutionized by research showing that many cases may not in fact come from the ovaries. For example, many high-grade serous tumors – the most common type – seem to start in the fallopian tubes, while some endometrioid and clear cell tumors may develop from endometriosis,” commented lead researcher Kezia Gaitskell of the University of Oxford (UK).
The researchers suggest that the risk reduction noted in women with more than one child could be related to infertility, as there are some conditions such as endometriosis that impact fertility and may also increase risk of specific types of ovarian cancer.
Discussing the results relating to tubal ligation, Gaitskell continued: “… it could be that tubal ligation acts as a barrier to help prevent the abnormal cells that might cause these tumors passing through the fallopian tubes to the ovaries. Our results are really interesting, because they show that the associations with known risk factors for ovarian cancer, such as childbirth and fertility, vary between the different tumor types.”