Abstract 4942: Serologic markers of infectious agents and ovarian cancer: Markers of prior Chlamydia trachomatis infection associated with increased ovarian cancer risk in two independent populations
Authors: Trabert Britton , Waterboer Tim , Coburn Sally B. , Brinton Louise A. , Sherman Mark E. , Lissowska Jolanta , Peplonska Beata , Hartge Patricia , Pawlita Michael , Wentzensen Nicolas 
Published: August 2018

Abstract
Background: Pelvic inflammatory disease (PID) has been associated with ovarian cancer and Chlamydia trachomatis (chlamydia) is the leading cause of PID in the developed world. Primary infection with chlamydia is often asymptomatic and may persist for several months/years, thus ascertainment of PID in epidemiologic studies is challenging due to pervasive misclassification and under-reporting. To improve our understanding of the role of chlamydia and other infectious agents in developing ovarian cancer, we evaluated serologic markers of infection with incident ovarian cancer using a staged approach in two independent populations.
Methods: Studies included: 1) a case-control study conducted in Poland of 278 ovarian cancer cases diagnosed from 2000 to 2003 and age- and study site-matched controls (n=556) and 2) a nested case-control study from the Prostate, Lung, Colorectal, and Ovarian (PLCO) Cancer Screening Trial including 160 women who eventually developed ovarian cancer and 159 matched controls. We calculated odds ratios (OR) and 95% confidence intervals (CI) for the association between serologic marker titers and ovarian cancer risk using logistic regression adjusted for matching factors and potential confounders. We evaluated laboratory cutpoints indicative of prior chlamydia infection and tested more stringent marker thresholds, identified in Poland and applied in PLCO, that could be relevant for a PID-like infection.
Results: In the Polish study, positivity for the chlamydia plasmid-encoded Pgp3 protein was associated with increased ovarian cancer risk [OR (95% CI): 1.63 (1.20-2.22)]; when a positive result was redefined at a higher titer, ovarian cancer risk increased [cutpoint 2: 2.00 (1.38-2.89); cutpoint 3 (max OR): 2.19 (1.29-3.73)]. All other chlamydia markers measured were associated with increased risk at the more stringent positivity threshold in Poland. In the prospective PLCO study, Pgp3 was associated with elevated risk at the laboratory cutpoint [1.43 (0.78-2.63)]; using higher thresholds, Pgp3 was associated with increased ovarian cancer risk [cutpoint 2: 2.25 (1.07-4.71); cutpoint 3: 2.53 (0.63-10.08)]. In both studies, markers of other infections (i.e., Mycoplasma genitalium, herpes simplex virus-2, human papillomavirus, herpes simplex virus-1, polyomavirus, hepatitis B, hepatitis C, Epstein Barr virus, cytomegalovirus) measured were not associated with risk.
Conclusions: In two independent populations, the gold standard serologic marker of prior/current chlamydia infection (Pgp3) was associated with a doubling in ovarian cancer risk, whereas markers of other infectious agents were unrelated. Although these findings need to be replicated, they suggest potential ovarian cancer risk reduction through targeted treatment of chlamydia infections.
Citation Format: Britton Trabert, Tim Waterboer, Sally B. Coburn, Louise A. Brinton, Mark E. Sherman, Jolanta Lissowska, Beata Peplonska, Patricia Hartge, Michael Pawlita, Nicolas Wentzensen. Serologic markers of infectious agents and ovarian cancer: Markers of prior Chlamydia trachomatis infection associated with increased ovarian cancer risk in two independent populations [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2018; 2018 Apr 14-18; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2018;78(13 Suppl):Abstract nr 4942.