Cancer antigen 125 level after a bilateral salpingo-oophorectomy: what is the contribution of the ovary to the cancer antigen 125 level?

Objective: Serum cancer antigen (CA) 125 is the only biomarker used frequently in women with or at risk for ovarian cancer. However, the same reference level is used before and after (prophylactic) bilateral salping-ooophorectomy (BSO). We evaluated the effect of BSO on CA125 level in BRCA mutation carriers and tested which factors interact with the change in CA125 level. Methods: All women who participated in the Nijmegen gynecological screening program and underwent prophylactic BSO were included. Information was obtained on age, smoking, menopausal state, previous hysterectomy and breast cancer, histopathological examination of the adnexa, hormone therapy use, and CA125 level before and after surgical operation. Ovarian volume was calculated. The logarithmic-transformed CA125 levels were used in a linear mixed model to study the relative change in CA125 level and possible interaction. Results: In 60 women, a relative decrease of 18% in CA125 level after BSO was found (P<0.01). The median serum CA125 level was 10.15 U/mL before and 8.36 U/mL after BSO. Menopausal state interacted with CA125 before and after the surgical operation (P<0.01). In addition, ovarian volume did not explain the difference in CA125 level (P = 0.94). Conclusions: BRCA mutation carriers show a relative decrease in CA125 level after BSO. Menopausal state interacts with CA125. Ovarian volume was excluded as a confounder. Possibly, the hormonal effect of ovaries plays a role in the CA125 level. Our study suggests that not the reference level of 35 U/mL but a lower level, as already suggested for postmenopausal women, should be applied to women after a salpingo-oophorectomy.