A study has revealed a possible link between an unhealthy vaginal microbiome and ovarian cancer. This means vaginas with low levels of protective bacteria, such as in bacterial vaginosis, aerobic vaginitis and in menopause, may be at greater risk.
There is currently no early screening test for ovarian cancer, so once the cancer is eventually detected, it is usually because it has spread to other organs and tissue and is causing symptoms. A pap test cannot detect ovarian cancer.
Researchers found that a vaginal and cervical microbiome low in healthy lactobacilli species was much more likely to correlate with ovarian cancer. The study participants were positive for the BRAC1 or BRAC2 gene mutations (without current cancer), those with ovarian cancer in various stages, and healthy controls.
One limitation of the study is that it was only on Caucasians, and other cohorts – who naturally have fewer lactobacilli species present in the vagina – need to be studied next.
What do bacteria have to do with ovarian cancer?
Microbes are responsible for many cancers, for example, the human papillomavirus (HPV) causes cervical and anal cancers. The number of cancers understood to be caused by microbes is increasing.
Ovarian cancer is more commonly diagnosed in those over 60, which is the hormonal stage whereby healthy lactobacilli species decline due to lowered levels of (or absent) oestrogen.
Oestrogen stimulates the production of ‘good bug food’, glycogen, from vaginal cells, which is then broken down by an enzyme into good-bug-bite-sized pieces. The more good bug food available, the more good bugs.
The researchers state: ‘The finding that the prevalence of community type L microbiota was lower in patients with ovarian cancer than in healthy controls, irrespective of disease stage, suggests that this reduced prevalence of type L microbiota could be causal rather than consequential.’
Meaning, the loss of healthy flora may cause (or contribute to) the development of cancer, rather than being the end result of cancer.
Does a microbe cause ovarian cancer?
There are several hypothesises with some research that supports the role of certain microbes in ovarian cancer.
An analysis of ovarian cancer tissue microbes with matched non-cancerous ovarian tissue showed that there were two species of bacteria found in the cancerous tissue, while not found in the non-cancerous tissue: Proteobacteria and Firmicutes.
These two microbes cause inflammation and release toxins that may directly damage cellular DNA. The exact mechanism proposed is double-stranded DNA breaks which go on to activate the DNA damage checkpoint pathway.
Unanswered questions on reducing the risk of ovarian cancer
- Can we intervene before or at menopause with microbe modulation (increasing, decreasing, keeping stable colonies of healthy flora) to help prevent ovarian cancer?
- Can tubal ligation (having fallopian tubes sealed off) limit the access of bacteria to the ovaries, and therefore help to prevent ovarian cancer?
- Does the oral contraceptive pill increase healthy flora for longer in fertile people entering menopause, and can the OCP be used to help prevent or reduce risks of ovarian cancer?
Symptoms of ovarian cancer you should be on the lookout for
The symptoms of ovarian cancer can be extremely subtle, and upon later reflection after diagnosis, may have been going on for some time.
- Bloating – minor to extreme
- Abdominal/pelvic discomfort
- Feeling tired and lethargic
- Lower pelvic pain
- ‘Niggles’ or twinges in the pelvis
- Feeling of pressure in the pelvis
- Frequent and/or urgent urination
- Changes in bowel habits
- Feeling of fullness after eating only a small amount
- Loss of appetite
- Digestive upset, such as indigestion
- Weight loss or gain (unexpectedly)
- Irregular periods
- Bleeding between periods
- Bleeding after menopause
- BRAC1 mutation
The EU’s tampon tax funded partially funded the research.
References1
- 1.Nené NR, Reisel D, Leimbach A, et al. Association between the cervicovaginal microbiome, BRCA1 mutation status, and risk of ovarian cancer: a case-control study. The Lancet Oncology. Published online August 2019:1171-1182. doi:10.1016/s1470-2045(19)30340-7
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