Comparison of CA-125 and Standard Definitions of Progression of Ovarian Cancer in the Intergroup Trial of Cisplatin and Paclitaxel Versus Cisplatin and Cyclophosphamide

Abstract

A definition for progression of ovarian cancer has been proposed based on either a confirmed doubling of CA-125 levels from the upper limit of normal or from the nadir level if levels are persistently elevated. Retrospectively, we determined whether the use of this CA-125 definition in a randomized trial would have shown the same magnitude of difference between the treatment arms as was shown when the standard progression definition was used. A retrospective analysis was performed on 680 patients in the Taxol Intergroup Trial with advanced epithelial ovarian carcinoma, of whom 628 were assessable according to CA-125. The date of progression according to clinical or radiologic criteria was compared with the date of progression according to CA-125. Of the 628 patients assessable for both definitions, 556 clinical or radiologic progressions were determined compared with 389 according to the CA-125 definition. There was a highly significant difference in the hazard of progression between the paclitaxel and cisplatin arm (TP) compared with the cyclophosphamide and cisplatin arm (CP) when either standard or CA-125 criteria were used to define progression (standard, P = .002; CA-125, P = .011). The hazard ratio of TP/CP over time was similar when comparing the different methods of defining progression. The results of this analysis show that the magnitude of the therapeutic benefit was similar whether CA-125 or standard criteria were used to define progression.