The role of CA 125 in screening for ovarian cancer.

Ovarian cancer has the worst prognosis of any gynaecological malignancy, primarily because it tends to present at an advanced stage. The excellent survival rates of early stage disease have provided the rationale for efforts to detect ovarian cancer early by screening, in the hope that survival rates will be improved. Available data suggests that CA 125 is elevated in the majority of epithelial ovarian malignancies prior to clinical presentation. Large trials of screening for ovarian cancer indicate that using a CA 125 cutoff value of 30 U/mL has good sensitivity, but inadequate specificity for detecting preclinical disease. Use of transvaginal ultrasonography as a second-line test in women with elevated CA 125 levels improves specificity to acceptable levels, as does use of a mathematical algorithm which analyses rates of change of CA 125. Two major randomised controlled trials, investigating the effect of screening strategies incorporating CA 125 on mortality, are currently underway.