CA-125 May Not Be Reliable Marker for Response to Doxil® In Ovarian Cancer
According to results presented at the 2005 annual meeting on Women’s Cancer™, early CA-125 levels were not consistently reliable as a measure of response to Doxil® (doxorubicin HCl liposome injection) in women with recurrent ovarian cancer.
Ovarian cancer is the most deadly form of gynecologic cancer. Since women are not routinely screened for ovarian cancer and the disease is not associated with specific symptoms, the majority of women are diagnosed once the cancer has spread from the ovary to distant sites in the body.
Doxil is a chemotherapy agent that is approved for the treatment of ovarian cancer that has progressed or recurred following prior therapy with chemotherapy agents referred to as platinum agents.
CA-125 is a “tumor marker” that can be detected in circulating blood. CA-125 levels are often elevated among women with ovarian cancer and among those whose cancer is progressing. Physicians frequently use levels of CA-125 to determine if treatment is working among women with ovarian cancer who are undergoing chemotherapy. However, CA-125 levels may not be the most appropriate marker for ovarian cancer since many cancers are not detected using this marker. As well, anticancer responses may not be adequately assessed using this marker.
A previous clinical trial was conducted to directly compare the chemotherapy agents Doxil and topotecan in women with recurrent ovarian cancer. This trial evaluated the CA-125 marker after the first and second cycles of chemotherapy to help determine a response to therapy. Researchers recently reviewed data from this trial and determined that early levels of CA-125 were not necessarily predictive of a patient’s anticancer response to chemotherapy.
- Among the patients who achieved a complete disappearance of detectable cancer (complete response) following treatment with Doxil, 50% had an increase in CA-125 level from the beginning of treatment (baseline) to the completion of their first cycle of Doxil.
- Among the patients who achieved a partial disappearance of detectable cancer (partial response) following treatment with Doxil, 41% had an increase in CA-125 levels from baseline to the completion of their first cycle of Doxil.
- By the end of the second cycle of chemotherapy, 19% of patients achieving a partial response to Doxil and 8% of patients achieving a partial response to topotecan had CA-125 levels above baseline.
- No patients who achieved a complete response following treatment with Doxil or topotecan had elevated CA-125 levels following their second cycle of chemotherapy.
- Among the patients who achieved a complete response to topotecan, 20% had an increase in CA-125 from baseline to completion of their first cycle of topotecan.
- Among the patients who achieved a partial response to topotecan, 8% had an increase in CA-125 levels from baseline to completion of their first cycle of topotecan.
Given these data, the researchers concluded that CA-125 does not appear to be a reliable means of measuring anticancer responses to Doxil or topotecan in recurrent ovarian cancer. The researchers state that further study is necessary to confirm these findings; however, it appears that more accurate ways to measure responses are needed.
Reference: Coleman R, Herzog T, Barter J, et al. Early increases in CA-125 after treatment with DOXIL or topotecan are not always reflective of response in patients with recurrent ovarian cancer. Proceedings from the 2006 annual Meeting on Women’s Cancer™. March 2006. Abstract 71.
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