Ovarian cancer is a malignancy that arises from various different cells within the ovaries. Ovarian cancer is the fourth commonest female cancer in Singapore.

Tumour markers are proteins that are produced by the human body in relation to cancer. Because advanced ovarian cancer is often associated with poor outcomes and early ovarian cancer is associated with significantly improved survival, a great deal of research is being done to explore how ovarian cancer could be detected earlier.

Approaches to screening include transvaginal sonography, serum markers, and two-stage strategies that use alterations in serum markers to prompt sonographic examination.

Among the serum markers, CA-125 has been studied most extensively. Isolated values of CA-125 lack adequate sensitivity or specificity, but when monitored over time, serial CA-125 values can achieve a specificity of 99.6%. However, sensitivity is limited and CA-125 may only be expressed by 80% of early-stage cancers.

Researchers from New York recently conducted a clinical study to compare a new marker, YKL-40, to the standard markers CA-125 in the detection of ovarian cancer. 2 This study included 190 women: 50 women who had been diagnosed with early ovarian cancer; 61 women who were at a high risk of developing ovarian cancer; 33 women with non-cancerous gynecologic conditions; and 46 women who were healthy.

Of the group of patients already diagnosed with ovarian cancer, 65% had elevated YKL-40 levels, while only 26% had elevated CA-125 levels. YKL-40 levels were highest in women with ovarian cancer and lowest in women who were healthy.

In addition, higher YKL-40 levels among the group of women with ovarian cancer conferred a significantly worse prognosis, compared to women with a lower YKL-40 level. It was concluded that YKL-40 might be a promising new marker in ovarian cancer, appearing to provide greater accuracy for early detection of ovarian cancer as well as long-term prognosis for patients already diagnosed with ovarian cancer, compared to CA-125.

However, further studies are required to provide definitive results and move YKL-40 into standard clinical practice. Till these larger studies become available, it would be safe to surmise that regular use of CA-125 should not be offered to general population as a screening test, due to the lack of its sensitivity as a screening test.

Reference:
Robert C. Bast, Jr. Status of Tumor Markers in Ovarian Cancer Screening. JCO 2003; 21: 200-205.
Dupont J, Tanwar M, Thaler H, et al. Early Detection and Prognosis of Ovarian Cancer Using Serum YKL-40. JCO 2004; 22: 3330-3339.

 

See Hui Ti
Associate Consultant
Medical Oncology
National Cancer Centre, Singapore