EXPONENTIAL REGRESSION OF CA 125 DURING SALVAGE TREATMENT OF OVARIAN-CANCER WITH TAXOL

The role of serum CA 125 in monitoring the response of epithelial ovar ian cancer to treatment has been extensively investigated. The exponen tial regression curve [ln(CA 125) = i + s (days after initiation of tr eatment)] has been reported to describe the rate of change of serum CA 125 during treatment. In this model, the y-axis intercept (i) represe nts the initial CA 125-secreting tumor burden, while the slope (s) is determined by the response to treatment. The exponential regression cu rve was calculated for 66 patients undergoing salvage chemotherapy wit h taxol. At a mean follow-up of 121 days, 50 (75%) patients had progre ssed and 35 (53%) had died. Stratification of the patients by stage, g rade, or histology did not reveal any significant differences in the r egression rate. When the patients were stratified by response, the mea n regression rate was 0.0157 +/- 0.011 for patients with progressive d isease (N = 19) vs -0.0250 +/-0.031 for those with stable disease (N = 25) and -0.0250 +/-0.015 for those with a partial response (N = 22) ( P < 0.0001). The regression rate did not correlate with progression-fr ee interval or survival (P > 0.05). We conclude that changes in serum CA 125 levels follow an exponential regression curve in patients under going salvage chemotherapy with taxol for progressive or recurrent ova rian cancer. A positive regression rate may predict which patients wil l progress prior to the time progression becomes clinically evident. H owever, a negative rate fails to provide discriminatory utility in pre dicting progression-free interval or survival. (C) 1994 Academic Press , Inc.