From the Guidelines
A CA125 level of 6000 U/mL is highly suggestive of ovarian cancer, with a specificity likely exceeding 98.5% in women over 50 years old, as indicated by a study published in the Annals of Oncology 1. This means that when CA125 is this dramatically elevated, there is a strong likelihood of ovarian cancer being present. While such a high CA125 level strongly suggests ovarian cancer, other conditions like endometriosis, pelvic inflammatory disease, menstruation, uterine fibroids, or benign cysts can occasionally cause significant CA125 elevations, though rarely to this extreme level. Some key points to consider include:
- The specificity of the CA125 test is lower in women under 50 years old, at 94.5% 1.
- A retrospective analysis of serum samples from 5550 women found that ovarian cancer was ultimately diagnosed in six women with elevated CA125 values, and also developed in three women with normal CA125 values 1.
- The use of multimodal screening, including serum CA125 measurement and ultrasound imaging, seems to be effective for early detection of ovarian cancer, with a higher specificity than transvaginal ultrasound alone 1. Definitive diagnosis still requires imaging studies (transvaginal ultrasound, CT, or MRI) and ultimately tissue diagnosis through surgery. The extremely high CA125 level would also serve as a useful baseline for monitoring treatment response if ovarian cancer is confirmed. Given the high specificity of a CA125 level of 6000 U/mL for ovarian cancer, particularly in women over 50 years old, immediate gynecologic oncology evaluation is warranted.
From the Research
CA125 Specificity for Ovarian Cancer
- The specificity of CA125 for ovarian cancer is not directly addressed in the provided studies for a value of 6000.
- However, study 2 estimated the probability of ovarian cancer at different CA125 levels and found that a CA125 value of 53 U/ml equated to a 3% probability of ovarian cancer overall.
- Study 3 compared the accuracy of CA125 measurements with CT scanning and TVUS in detecting recurrent tumors and found that the specificity of CA125 measurements was 100% at cut-off limits of 16 and 35 U/ml.
- Study 4 found that a CA125 level of 12 U/mL after completing adjuvant chemotherapy was an independent prognostic factor predictive for disease progression in patients with high-risk, early stage epithelial ovarian cancer.
Factors Affecting CA125 Specificity
- Age is a factor that affects the specificity of CA125 for ovarian cancer, with study 2 finding that the estimated probability of ovarian cancer varied by age.
- The type of ovarian cancer also affects the specificity of CA125, with study 5 noting that type II ovarian cancers are usually diagnosed in advanced stages and have significantly higher CA125 levels than type I tumors.
- Study 6 noted that CA125 is not sufficiently reliable in diagnosis to screen for early-stage ovarian cancer, but it has been a valuable indicator for evaluating chemotherapeutic efficacy and prognosis.
CA125 Cut-Off Values
- Study 3 suggested a cut-off limit of 16 U/ml for CA125 to detect recurrent serous ovarian adenocarcinoma.
- Study 2 found that a CA125 value of 53 U/ml equated to a 3% probability of ovarian cancer overall.
- Study 4 found that a CA125 level of 12 U/mL after completing adjuvant chemotherapy was an independent prognostic factor predictive for disease progression in patients with high-risk, early stage epithelial ovarian cancer.