Circulating tumor cells (CTC) in a study of relapsed/recurrent advanced ovarian cancer: An exploratory analysis in the ova-301 phase III study of pegylated liposomal doxorubicin (PLD) compared with trabectedin and PLD

Abstract

5551 Background: Circulating tumor cells (CTC) have demonstrated predictive and prognostic value among patients with metastatic breast, colorectal, and prostate cancer. In a phase III study of pegylated liposomal doxorubicin (PLD) with trabectedin (T) vs PLD for relapsed ovarian cancer, we assessed the affect of CTCs on progression free survival, (PFS) and overall survival (OS). Methods: CTCs were isolated from peripheral blood (10 mLs) using the CellSearch system and reagents (Veridex). A CTC is defined as EpCAM+, cytokeratin+, CD45-, and is positive for the nuclear stain DAPI. The normal reference range for CellSearch is < 2 CTC/7.5 mLs of blood. Hazard ratios adjusted for known prognostic factors were estimated by Cox regression. Results: 216 subjects had baseline CTC measurements of which 111 (51.4%) were randomized to the PLD+T arm; 143/216 patients (66.2%) were platinum sensitive. Thirty-one/216 patients (14.4%) had 2 or more CTCs detected prior to the start of therapy (range 2–566). Univariate Cox regression analyses indicated that patient's > 2 CTCs prior to therapy have 1.89 (p = 0.003) and 2.06 (p = 0.003) fold higher risk for progression and death respectively. Multivariate analyses that include baseline CTC, baseline CA125, platinum sensitivity status, largest diameter lesion, number of tumor lesions, ECOG PS, age, tumor histology, tumor grade and prior taxane show that patients with elevated baseline CTC have 1.58 (p = 0.058) and 1.54 (p = 0.096) fold higher risk for progression and death respectively. Conclusions: Results from this study indicate that although CTC detection in blood from relapsed recurrent ovarian cancer patients is relatively low, elevated numbers of CTCs imparts an unfavorable prognosis for patients. Multivariate analysis indicates that CTCs have prognostic value that is independent of established factors and thus provides a clinically useful tool for assessing prognosis in this difficult to treat patient population. [Table: see text]