CA125 blood test may be superior to standard imaging techniques like CT scans

A new study shows that the CA125 blood test, which measures the level of protein produced by ovarian cancer cells in the blood, may be superior to standard imaging techniques like CT scans in predicting survival in patients with recurrent ovarian cancer.

The study, to be published online September 13 in the Journal of Clinical Oncology, is the first to compare the two procedures with respect to survival.

"This is good news for patients – our study indicates that selected patients can be safely monitored by blood tests alone and thus avoid costly and time consuming CT scans," said Bo Gronlund, MD, lead author and head of the CODOVA database at the Department of Oncology at Rigshospitalet, the Copenhagen University Hospital.

CT scans and other imaging techniques are often used in patients with recurrent cancer to assess whether the patient is responding to treatment. RECIST, the standard criteria for analyzing CT scans and ultrasonography, assesses treatment response by measuring the growth or shrinkage of the tumor.

However, unlike other solid tumors, ovarian cancer spreads diffusely through the abdomen, making tumor tissue much more difficult to detect through CT scans. As a result, response cannot always be measured by RECIST criteria.

Researchers hypothesized that the CA125 blood test might be a better tool for observing tumor growth among patients whose cancer has returned than traditional imaging techniques. To compare the two procedures, they used the RECIST criteria and a set of criteria for the CA125 blood test, which assesses treatment response according to the level of CA125 protein present in the blood.

Using one of the world's largest database of patients with recurrent ovarian cancer, researchers retrospectively studied 131 patients receiving topotecan or paclitaxel-carboplatin as a second-line chemotherapy. Researchers found that the CA125 criteria were 2.6 times more accurate than RECIST in predicting survival, and concluded that in selected patients, tumor-marker guided response criteria like CA125 may be superior to imaging-based response criteria in predicting the outcome of second-line chemotherapy.

However, researchers noted that the study findings are only applicable to patients treated with topecan or paclitaxel-carboplatin, and pointed to the need for a randomized trial that includes additional chemotherapy agents or novel targeted therapies and that assesses CA125 and RECIST criteria in predicting both survival and quality of life.

An accompanying editorial by Professor Gordon J.S. Rustin of Mount Vernon Cancer Centre in Middlesex, UK underscored the importance of determining which response criteria is the more reliable method for predicting survival and clinical benefit.

"The CA125 response criteria has great potential value in clinical trials. Increased confidence in a CA125 response definition should lead to a cheaper, and in some cases, more accurate method for monitoring ovarian cancer therapy than standard radiographic criteria," he said.

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