Predictive value of serum CA125 levels in women with persistent or recurrent epithelial ovarian cancer (EOC) or primary peritoneal cancer (PPC) treated with bevacizumab (Bev) on a Gynecologic Oncology Group (GOG) phase II trial

e16505 Background: The clinical utility of serum CA125 in patients (pts) with EOC/PPC treated with biologic agents is unknown. The primary objective of this study was to determine the proportion of pts treated with bevacizumab on a phase II clinical trial with stable disease by RECIST who demonstrated disease progression (pgrn) as assessed by modified GCIG CA125 criteria. Methods: Sixty-two pts with measurable recurrent or persistent EOC/PPC were treated with bevacizumab 15 mg/kg Q 21 days on a phase II clinical trial. Primary endpoints of the clinical trial were progression-free (PF) survival at 6 months and response assessed by RECIST criteria. Pts were removed from therapy/evaluation for disease prgn by RECIST, toxicity, or by subject request. Serum CA125 was collected at entry and prior to each cycle but levels were only used to define a complete response which required CA125 normalization (≤35). Modified GCIG criteria were retrospectively applied to these CA125 values to determine time to progression from date of entry to either the first time CA125>70 for pts whose CA125 normalized on treatment or was greater than 2X the nadir value for pts whose CA125 did not normalize. Censored cases provided time until the date of last CA125 measurement. Results: The median PFS by RECIST was 4.7 mos. Of those patients who had prgn by CA125, the median residual time to prgn by RECIST was 1.4 mos. In all, twenty-five (40.3%) pts survived PF for 6 mos. by RECIST and 16 (25.8%) by CA125. Ten pts who survived PF for at least 6 mos. by RECIST indicated treatment failure before 6 mos. by CA125, or 40% of the 25 positive outcomes. Eight pts continued to receive treatment for at least 4 mos. after prgn by CA125, with one continuing therapy for more than 3 years. Conclusions: Serum CA125 levels were a useful marker of progression in some pts treated on this trial; however, some pts received clinical benefit from continued therapy in spite of indications of disease prgn by CA125. Consideration should be given before discontinuing bevacizumab therapy based on CA125 progression alone. No significant financial relationships to disclose.