Serum carcinoembryonic antigen (CEA) in the management of advanced colorectal cancer (ACRC) treated with CAPIRI plus bevacizumab.

Abstract

e14049 Background: Although in use for almost 30 years, the clinical value of CEA as the marker of choice for monitoring the response of advanced colorectal cancer (ACRC) to systemic therapy is not clearly established and no study has investigated the usefulness of CEA in patients (pts) treated with new drugs as angiogenesis inhibitors. The aim of this study was to prospectively evaluate the relationship between serum CEA, and computed tomography (CT) scan, gold standar test, in patients with ACRC by calculating sensitivity (S), specificity (Sp), positive predictive value (PPV), and negative predictive value (NPV). Methods: 150pts with previously untreated histopatologically confirmed ACRC, age > 18 years and Karnosky (PSK) ≥ 60% were treated with capecitabine, irinotecan and bevacizumab, in a 3-week cycle. Response was evaluated every 2-3 month by CT scan, CEA was checked on day 1 of every cycle. Response by tumour marker was defined as a reduction of 50%, and progression as an increase of 30%. Results: From March 2005 to July 2009, 150 pts entered in the study. 111 pts have progressed to first line treatment and 71 have died. CEA was 2x upper normal limit (UNL) in 109 (72%), 5x UNL in 88 (58%), inferior a 2x ULN in 41 (28%), and normal (< 5 ng/mL) in 28 (18%) pts. 17 pts with normal baseline CEA have progressed, and CEA increased in 14 (82%) during progressive disease. For response, there were 57 pts truly positive (TP), 45 truly negative (TN), 31 false-positive (FP), and one false-negative (FN) pts (Chi-square 48.2, p < 0.0001) so response resulted in S of 98% (CI 95%, 0.90-0.99), Sp of 59%, (CI 95%, 0.47-0.70) PPV of 64.7%, and NPV of 97%. For progression, there were 101 TP, 84 TN, 44 FN, and no FP pts (Chi- square 158.5, p < 0.0001) so progression resulted in S of 90.9% (CI 95%, 0.84-0.95), Sp of 100% (CI 95%, 0.95-1), PPV of 100%, and NPV of 65.6%. CEA indicated progression with a median of 6 weeks prior to the CT scan and response with a median of 3 weeks prior to CT scan. Conclusions: CEA is an accurate, simple, accessibility, low cost and robust method and these results suggest that CEA analysis could help in the decision of accelerate or delay CT scan in order to avoid un-useful treatments/CT scan. No significant financial relationships to disclose.