Serum tumour marker CA 125 in monitoring of ovarian cancer during first-line chemotherapy.

The value of the serum tumour marker CA 125 to date has been in the monitoring of ovarian cancer patients for response to therapy and for recurrence of disease. However, despite the availability of serial data on CA 125, the problem of interpreting a change over time is still unsolved. The aim of this study was to assess the ability of CA 125 to monitor patients with ovarian cancer during postoperative chemotherapy. 255 patients with stage IC-IV ovarian cancer were allocated to the tumour marker monitoring study. The evaluation of CA 125 information was based on the analytical imprecision, the normal intra-individual biological variation, the sampling interval, and the cut-off value. Additionally, a new assessment criterion based upon an increment of 2.5 times the baseline CA 125 concentration confirmed by a third measurement was elaborated and the utility investigated. The efficiency of CA 125 for identifying progression and non-progression during first-line chemotherapy was 91.9%. The median lead time for true positive results was 41 days. Using the new elaborated criterion the efficiency of CA 125 for identifying progression and non-progression during first-line chemotherapy was 90.5%. The median lead time for true positive results was 35 days. CA 125 gave reliable prediction of progressive disease during postoperative chemotherapy. The results indicate a high applicability of the presented progression criteria during CA 125 monitoring of patients with changing activity of ovarian cancer. Copyright 2001 Cancer Research Campaign.