Extreme drug resistance assay and response to chemotherapy in patients with primary peritoneal carcinoma

Background and Objectives The extreme drug resistance (EDR) assay is an in vitro chemoresistance assay performed on tumor samples grown in culture and is claimed to predict drugs unlikely to produce response. Its clinical value in patients with epithelial ovarian cancer (EOC) has recently been questioned. The aim of this study is to describe EDR assay results and responses to chemotherapy among women with primary peritoneal adenocarcinoma (PPA) and to compare them with those of women with EOC. Methods Fresh tumor specimens from 20 consecutive women with PPA were tested for EDR to the following drugs: cisplatin, carboplatin, paclitaxel, doxorubicin, cyclophosphamide, ifosfamide, etoposide, hexamethylmelamine, and topotecan. They were then treated with cisplatin-based combination chemotherapy. The results of the EDR assay and response to chemotherapy were compared with those among women with EOC. Results There was no significant difference in the incidence of EDR to cisplatin, carboplatin, paclitaxel, doxorubicin, cyclophosphamide, ifosfamide, etoposide, hexamethylmelamine, and topotecan among patients with PPA and those with EOC. The response rate of PPA patients to chemotherapy was 80.0% and unrelated to EDR to the individual drugs used in combination chemotherapy. Conclusions The EDR profile and response to cisplatin-based chemotherapy among women with PPA were similar to those among women with EOC. These findings support treating both conditions similarly. EDR to individual drugs does not preclude response to combination chemotherapy. J. Surg. Oncol. 2000;73:148–152. © 2000 Wiley-Liss, Inc.