Chlamydia may be linked to an increased risk of ovarian cancer, according to research presented at the American Association for Cancer Research’s annual meeting. Findings show that an antibody present in the blood of women previously infected with the sexually transmitted infection (STI) appears to be associated with almost double the risk of ovarian cancer, an AACR press release reports

Chlamydia is currently the most commonly reported STI in the United States. The bacterial infection is also linked to pelvic inflammatory disease, which previous research has also shown is linked to an increased risk of ovarian cancer. However, until recently, little research had been conducted on the potential links between chlamydia and the disease. 

For the study, researchers examined data from two different studies on the topic: a Polish study of 278 women diagnosed with ovarian cancer between 2000 and 2003 and 556 matched controls as well as the Prostate, Lung, Colorectal and Ovarian Cancer Screening Trial, which was sponsored by the National Cancer Institute (NCI). That study included 160 women diagnosed with ovarian cancer and 159 matched controls. 

Using a statistical model called logistic regression, researchers analyzed the data by calculating odds ratios for the association between chlamydia antibodies (which appear in the body after someone is infected) and ovarian cancer risk. They ultimately found that women who had chlamydia antibodies were twice as likely to be diagnosed with ovarian cancer. The study also evaluated antibodies against several other STIs, including human papillomavirus (HPV), herpes simplex virus, hepatitis B virus (HBV) and hepatitis C virus (HCV) but found no association.

Researchers say the next step is to confirm these findings in larger study populations. There’s also the matter of whether or not certain chlamydia infections are more specifically tied to different subtypes of ovarian cancer. 

“We need to understand more about what causes ovarian cancer so that we can improve screening and treatment and ultimately improve survival rates,” said the study’s lead author Britton Trabert, PhD, MS, an investigator in the NCI’s Division of Cancer Epidemiology and Genetics. Ovarian cancer is a relatively rare cancer, but women who develop it often face poor survival rates. 

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