Determination of a second-line chemotherapy agent for patients with colorectal cancer (CRC) after fluorouracil failure

Abstract

3638 Background: Fluorouracil-based chemotherapy, such as with 5-FU/leucovorin, is standard as first-line chemotherapy for advanced CRCs. However, the best agent for chemotherapy after fluorouracil failure is still unknown. The primary objective of this study was to determine the best agent for second-line chemotherapy. Methods: Seventy-eight tumor specimens from CRC patients with no prior chemotherapy were obtained operatively and their sensitivity against five anticancer drugs, 5-FU, Mitomycin C, Cisplatine, Decetaxel and CPT-11, in an in vitro chemosensitivity test using CD-DST methods was analyzed. The chemosensitivity was expressed as the percentage T/C ratio, where T was the total volume of the treated group and C was that of the control group. Pearson's correlation coefficients were used to assess the relationship. P<0.05; statistically significant. A statistically significant correlation between two drugs was defined as a correlation of cross-resistance between them. Conversely, non-positive correlation was defined a correlation of no cross-resistance between them, with each of them having an independent spectrum. Results: Fifty-four specimens (colon, 30; rectum, 24) were successfully analyzed. The mean T/C ratios of 5-FU, Mitomycin C, Cisplatine, Decetaxel and CPT-11 were 79.1%, 69.9%, 81.2%, 59.4% and 63.8%, respectively. Although each of the agents has a different functional mechanism from that of 5-FU, with the exception CPT-11, all of them had a closely positive correlation with 5-FU. Conclusions: Only CPT-11 expressed an independent spectrum from 5-FU, thus indicating it to be the best agent for second-line chemotherapy after fluorouracil failure. No significant financial relationships to disclose.