Significance of Early Changes in the Serum CA-125 Antigen Level on Overall Survival in Advanced Ovarian Cancer

Objective: The relationship between survival and early changes in the serum level of the CA-125 antigen in patients with advanced ovarian cancer remains poorly defined.

Methods: To explore this issue, the serum CA-125 values from 101 patients with advanced ovarian cancer who participated in a Southwest Oncology Group trial (SWOG 8412), which compared the systemic delivery of cisplatin/cyclophosphamide vs. carboplatin/cyclophosphamide (both delivered every 28 days for 6 cycles) in suboptimal residual stage III and IV ovarian cancer, were evaluated. All patients in this analysis had CA-125 values available for at least 8 weeks following initiation of chemotherapy. Cox proportional hazards regression was used in multivariate analysis to determine the prognostic significance of the CA-125 concentration.

Results: While pretreatment CA-125 values did not correlate with survival, the concentration of this tumor marker 8 weeks after initiation of therapy was a powerful independent prognostic factor. The median survivals for patients (n = 51) with a CA-125 < 35 U/ml, vs. patients (n = 50) with a CA-125 > 35 U/ml, at this time point, were 26 months and 15 months, respectively (P = 0.0001). Further, women with serum CA-125 values <50% of their pretreatment concentration at 8 weeks experienced a median survival of 21 months, compared to only 10 months for individuals with tumor marker levels >50% of their baseline value (P = 0.0003).

Conclusion: Reduction in the serum CA-125 concentration over the initial two cycles of platinum-based chemotherapy is a powerful independent predictor of survival for patients with suboptimal stage III or IV ovarian cancer. Patients without significant declines in CA-125 after two cycles of platinum-based chemotherapy have a particularly poor prognosis.