Correlation between CA-125 serum level and response by RECIST in a phase III recurrent ovarian cancer study

ObjectivesTo evaluate in a large phase III recurrent ovarian cancer trial (OVA-301): 1) the concordance between CA-125 level vs. best overall response (OR) and progression-free survival (PFS) determined by radiological assessment 2) the impact of early CA-125 changes over the subsequent radiological response, and 3) the prognostic value of CA-125 response and CA-125 PFS to predict radiological response and PFS.MethodsAssessment of response in the entire randomized population was performed by the Response Evaluation Criteria in Solid Tumors 1.0 (RECIST) and modified Rustin criteria for CA-125 determination.ResultsMost CA-125 decreases were observed in RECIST responders (82% of patients treated with the combination and 74% in the PLD alone). CA-125 progression preceded RECIST progression in 35% of patients with a median lead time of 8.4 weeks. A high concordance rate between CA-125 PFS status at 4 months (PFS4) and CA-125 response as a predictor of PFS4 (87%) and radiological response (79%) was found in the combination, with high positive predictive value for radiological PFS4 (92%) and high negative predictive value for OR (90%). An early CA-125 decrease was predictive for the ultimate response since it was found in a high rate of RECIST responders.ConclusionRadiological response was preceded by a favorable predictive CA-125 decrease in a high proportion of patients, suggesting that CA-125 evaluation may be an appropriate tool for tumor assessment in patients with ovarian cancer.

Research highlights
► We evaluate the concordance, prognostic value and impact of early CA-125 changes vs. RECIST response in recurrent ovarian cancer.
► CA-125 monitoring is a useful surrogate marker of efficacy.
► CA-125 expression in recurrent ovarian cancer can be used as a decision tool to evaluate the utility of chemotherapy continuation.