Role of Conventional Chemosensitivity Test and Tissue Biomarker Expression in Predicting Response to Treatment of Peritoneal Carcinomatosis From Colon Cancer Chiara Arienti, 1 Anna Tesei, 1 Giorgio Maria Verdecchia, 2 Massimo Framarini, 2 Salvatore Virzì, 3 Antonio Grassi, 3 Emanuela Scarpi, 1 Livia Turci, 1 Rosella Silvestrini, 1 Dino Amadori, 1 Wainer Zoli 1 Abstract Peritoneal carcinomatosis (PC) is observed in approximately 10% of patients with colorectal cancer at the time of primary cancer resection. Most of these patients receive 5-fluorouracil (5-FU)- or oxaliplatin-contain- ing chemotherapy regimens as first-, second-, or third-line treatment. In the present study, sensitivity and resistance to drugs used to treat PC were better defined by a conventional chemosensitivity test than by biomarker expression. Background: 5-Fluorouracil- or oxaliplatin-based regimens are the treatments of choice in patients with PC from colon cancer. There are currently no useful preclinical evaluations to guide the decision-making process for tailored therapy. The aim of the present study was to compare the advantages and limits of a conventional in vitro chemosensitivity test with those of a panel of biomolecular markers in predicting clinical response to different drugs used to treat colon cancer-derived PC. Patients and Methods: Fresh surgical biopsy specimens were obtained from 28 patients with peritoneal carcinomatosis from colon cancer. TS, TP, DPD, MDR1, MRP-1, MGMT, BRCA1, ERCC1, GSTP1, and XPD gene expression levels were determined by real-time reverse transcription polymerase chain reaction. An in vitro chemosensitivity test was used to define a sensitivity or resistance profile to the drugs used to treat each patient. Results: Expression levels of the genes analyzed were generally poorly related to each other. TS and ERCC1 expression was inversely related to response to 5-FU-and/or oxaliplatin-containing regimens. Significant predictivity in terms of sensitivity but poor predictivity of resistance (56.2%) (P = .037) were observed for ERCC1 expression (90%), and high predictivity of resistance (100%) but very low predictivity of sensitivity (40%) (P = .014) were registered for TS. The best overall and significant predictivity was observed for chemosensitivity test results (62.5% sensitivity and 89% resistance; P = .005). Conclusions: Sensitivity and resistance to drugs used in vivo was better defined by the chemosensitivity test than by biomarker expression. Clinical Colorectal Cancer, Vol. 12, No. 2, 122-7 © 2013 Elsevier Inc. All rights reserved. Keywords: Colon cancer, ERCC1, In vitro chemosensitivity test, Peritoneal carcinomatosis, Response prediction, TS Introduction Colorectal cancer is the second leading cause of cancer death in North America and Western Europe. 1 The advent of new, effective chemotherapeutic agents in clinical practice has increased median survival by up to 20 months in advanced disease. This result, how- ever, is not obtainable in patients with peritoneal carcinomatosis (PC), which despite advances in the early detection of the primary tumor, is still observed in approximately 10% of patients at the time 1 Biosciences Laboratory, IRCCS Istituto Scientifico Romagnolo per lo Studio e la Cura dei Tumori (IRST), Meldola, Italy 2 Department of Surgery and Advanced Cancer Therapies, Morgagni-Pierantoni Hospital, Forlì, Italy 3 Department of Surgery, Bentivoglio Hospital, Bologna, Italy Submitted: Jul 25, 2012; Revised: Oct 2, 2012; Accepted: Nov 26, 2012; Epub: Jan 16, 2013 Address for correspondence: Wainer Zoli, PhD, IRCCS Istituto Scientifico Romagnolo per lo Studio e la Cura dei Tumori (IRST), via Maroncelli 40, 47014 Meldola (FC), Italy Fax: +39-0543-739221; e-mail contact: w.zoli@irst.emr.it Original Study 122 Clinical Colorectal Cancer June 2013 1533-0028/$ - see frontmatter © 2013 Elsevier Inc. All rights reserved. http://dx.doi.org/10.1016/j.clcc.2012.11.006