SEATTLE--In patients with advanced epithelial ovarian cancer, CA 125 concentrations after two cycles of chemotherapy are a powerful independent predictor of survival, a Southwest Oncology Group Study (SWOG) has shown.
SWOG statistician Ping-Yu Liu, PhD, and his colleagues obtained baseline and follow-up CA 125 levels for 101 patients enrolled in a phase III SWOG study. All patients had suboptimal stage III or IV ovarian cancer and were receiving chemotherapy--either cisplatin(Drug information on cisplatin) (Platinol) or carboplatin(Drug information on carboplatin) (Paraplatin) plus cyclophosphamide(Drug information on cyclophosphamide)--every 28 days for six cycles.
"We found that patients with lower CA 125 values at 8 weeks had a significantly higher chance of longer term survival," said Dr. Liu of the SWOG Statistical Center and Fred Hutchinson Cancer Research Center.
Of the 101 patients, 51 had a CA 125 level less than 35 U/mL (the cutoff for normal) 8 weeks into the study, ie, 4 weeks after the second course of chemotherapy. Median survival for these patients whose CA 125 levels had normalized by 8 weeks was 26 months, compared with 15 months for the other 50 patients whose CA 125 values remained above 35 U/mL.
Similarly, for patients whose CA 125 values declined by 50% or more from their pretreatment level, median survival was 21 months versus 10 months for those whose values increased or dropped by less than 50%.
"So overall, patients whose CA 125 values either normalized or were reduced by 50% or more had an 11 month increase in their median survival," Dr. Liu said.
Further analysis showed that other prognostic factors, such as age, performance status, and disease stage, could not explain the survival difference between those patients with lower and higher CA 125 values. "In fact, at 8 weeks, CA 125 turned out to be the single most significant prognostic factor for survival," he said.