P-291 In women with endometriosis, effective treatment of chronic endometritis with antibiotics lowers serum CA-125 levels

Abstract Study question To evaluate the effect of chronic endometritis treatment on serum CA-125 levels in women with endometriosis. Summary answer Cure of chronic endometritis leads to a reduction in serum Ca-125 levels in women with endometriosis. What is known already Endometriosis is a chronic inflammatory disease characterized by the ectopic growth of endometrial tissue outside the uterine cavity. It is hypothesized that the disease exerts direct inflammatory effects on the ovaries, fallopian tubes, and the eutopic endometrium. In endometriosis, CA-125 levels are often elevated. Literature reports a frequent coexistence of endometriosis and chronic endometritis (CE) in women undergoing hysterectomy for benign indications. CE, characterized by macroscopic and histological alterations of the endometrium, was present in 38.5%-42.3% of women with endometriosis, compared to lower prevalence rates in controls infertile patients without endometriosis, supporting a potential etiopathogenic link between endometriosis and CE. Study design, size, duration This retrospective case-control study was conducted at the Department of Obstetrics and Gynecology, University of Bari. The study included 51 patients suffering of both ovarian endometriosis and CE. The primary objective was to investigate whether CE cure modifies serum CA-125 levels among women with ovarian endometriosis. The secondary objective was to assess any modifications in the size of endometriotic cysts following the cure of CE. Recruitment period was from September 2021 to February 2023. Participants/materials, setting, methods All patients received antibiotic therapy (100 mg of doxycycline, twice daily for ten days) and, the following month, hysteroscopy with control biopsy. Of these, 36 women were cured of chronic endometritis (Group A), while 15 women showed persistent disease (Group B). Endometriosis was diagnosed by transvaginal ultrasound and chronic endometritis through hysteroscopy, histology, and immunohistochemistry for CD138. Serum CA-125 levels were measured before antibiotic therapy and approximately 3 months later. Main results and the role of chance The primary outcome was to compare the change in CA-125 values between women cured of chronic endometritis and women with persistent disease. There were no statistically significant differences in baseline characteristics between the groups (p=ns). The majority of patients in both groups had a single ovarian endometrioma and the micropolypoid endometrial appearance was the predominant finding of chronic endometritis observed during hysteroscopy in both Groups. In Group A, the mean CA-125 value significantly decreased after antibiotic therapy from 58.56 U/mL (± 32.45) to 38.25 U/mL (± 17.31) (p < 0.001). No significant changes in CA-125 values were observed in Group B before and after antibiotic therapy (69.70 ± 27.42 versus 67.47 ± 24.52 U/mL, p=ns). The absolute change in CA-125 values was significantly greater in terms of reduction in Group A compared to Group B (-20.31 ± 27.09 versus -2.13 ± 12.51 U/mL; p = 0.02). Adjustment for confounders in a multivariable regression model revealed that the cure of chronic endometritis was independently associated with a significant decrease in absolute serum CA-125 levels (p = 0.006). Cyst size did not significantly change after antibiotic therapy in both groups (p=ns). Limitations, reasons for caution The main weakness of our study is that CA-125 was only measured once before and once after treatment of CE with a course of antibiotics. Moreover, our study does not allow for inferences regarding the impact of the observed reduction in serum CA-125 on the subjective symptoms related to endometriosis. Wider implications of the findings Our study constitutes the first demonstration that effective treatment of CE results in a significant decrease in a non-invasive marker of endometriosis, CA-125 supporting the emerging concept that the endometriosis might have an infectious origin. Trial registration number not applicable