CA-125 HALF-LIFE IN OVARIAN-CANCER - A MULTIVARIATE SURVIVAL ANALYSIS

Serum CA 125 regression after cytoreductive surgery and during the fir st three courses of chemotherapy was studied in 60 ovarian cancer pati ents and compared to known prognostic factors. Various methods reporte d in the literature to calculate a CA 125 half-life value were compare d. Using two exponential regression models (Van der Burg et al., 1988; Buller et al., 1991), mean half-lives in stage I-II patients after co mplete cytoreductive surgery were respectively 10.7 days (range: 5-23) and 9.8 days (range: 7-15). Within stage III-IV patients, a significa nt positive correlation was seen between survival and (a) stage III (P = 0.002), (b) residual tumour less-than-or-equal-to 1 cm (P = 0.02), (c) CA 125 normalisation after three courses (P = 0.003) and (d) CA 12 5 half-life less-than-or-equal-to 20 days (P = 0.02-0.004, depending o n the method used for half-life calculation). The median survival time s of patients with and without a CA 125 normalisation after three cour ses were 27 and 14 months respectively (P = 0.003). When using the mod el of Buller et al. patients with a CA 125 half-life less-than-or-equa l-to 20 days had a median survival of 28 months compared to a median s urvival of 19 months for patients with CA 125 half-lives > 20 days (P = 0.004). Half-life calculations only showed a significant correlation with survival, if pre-surgery CA 125 levels were used as a baseline. In a survival analysis using the Cox proportional hazards model, stage of disease was the most predictive variable for survival (P = 0.006). The only additional independent prognostic factor for survival was th e CA 125 half-life calculated according to Buller [derived from the fo rmula: CA 125 = exp. [i-s x (days after surgery)], in which i is the y -axis intercept and s is the slope of the CA 125 regression curve]. A CA 125 half-life less-than-or-equal-to 20 days vs >20 days calculated using this formula, provides an independent prognostic factor for surv ival in stage III-IV patients early in the course of therapy (P = 0.04 ).