Ovarian cancer risk linked to missing bacteria

Lower levels of a protective bacteria put women at greater risk of developing ovarian cancer, a study suggests

Women at high risk of developing ovarian cancer have lower levels of protective ‘friendly’ vaginal bacteria, as do women diagnosed with the disease, a study suggests.

Changes in the number of healthy bacteria, called lactobacilli, which normally help prevent overgrowth of other ‘unfriendly’ types of bacteria, can be used to build a clearer picture of a woman’s risk of developing ovarian cancer, according to the study, led by University College London’s EGA Institute for Women’s Health.

Women with ovarian cancer had a significant reduction in vaginal lactobacilli, the researchers found. This reduction was also seen in women with a 40 times higher risk of developing ovarian cancer in their lifetime due to inheriting a BRCA1 gene mutation.

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The younger the women the more apparent was the reduction in lactobacilli, both for women with ovarian cancer and those at higher risk.

Bacteria naturally found in the vagina create a protective barrier to infections that stops them travelling up the gynaecological tract to the fallopian tubes and ovaries. If an infection travels up the gynaecological tract it can cause pelvic inflammatory disease and lead to issues such as infertility.

Infections that influence cancer and gynaecological issues

Evidence suggests that these infections can influence the development of ovarian cancer and other gynaecological issues.

During the study, samples were taken from the cervix and vagina of 176 women who were eventually diagnosed with ovarian cancer, 109 women who were at high risk of developing ovarian cancer in their lifetime because they were carriers of an inherited BRCA1 mutation, and 295 women who were not at a higher risk of developing the disease.

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The samples were taken using a standard cervical screening brush, and were analysed using next-generation sequencing.

Young women at higher risk of developing ovarian cancer due to having a mutant BRCA1 gene had nearly three times less lactobacilli in their vagina compared with those who did not carry the mutant gene. The women within this group who also had a close family member with ovarian cancer were even more likely to lack lactobacilli.

Over one quarter of young women under the age of 30 with a BRCA1 mutation had low numbers of lactobacilli, but none of their peers without a BRCA1 mutation had reduced lactobacilli.

Reference

Nené N, Reisel D, Leimbach A et al (2019) Association between the cervicovaginal microbiome, BRCA1 mutation status, and risk of ovarian cancer: a case-control study Lancet Oncology. doi: 10.1016/S1470-2045(19)30340-7