An anticancer drug sensitivity test to determine the effectiveness of UFT as postoperative adjuvant chemotherapy for patients with stage III colorectal cancer.

Background: Tissue samples from patients with pathologic ((p)) stage III colorectal cancer were tested for sensitivity to 5-fluorouracil (5-FU). On the basis of the results, patients were divided into 5-FU-sensitive and 5-FU-resistant groups, and both groups were treated with fluoropyrimidine (UFT) as postoperative adjuvant chemotherapy. Recurrence, 5-year survival rates, and 5-year recurrence-free survival rates were compared.
Methods: The anticancer sensitivity test described in this study was carried out using tumor samples obtained surgically from 34 patients with curatively resectable colorectal cancer that had been diagnosed definitively as (p)stage III (IIIa, 23 patients; IIIb, 11 patients). Regardless of tumor sensitivity or resistance to 5-FU, all 34 patients were subsequently treated daily with UFT at 300 mg/day as postoperative adjuvant chemotherapy. Treatment was initiated 3 weeks after surgery and continued for 2 years.
Results: Of the 34 patients with (p)stage III colorectal cancer, the tumors of 16 (47%) were 5-FU-sensitive (S group) and 18 (53%) were 5-FU-resistant (R group). The recurrence rates in the S and R groups following postadjuvant therapy with UFT were 25% and 61%, respectively, which is a significantly lower response in the S group (P = .045). The odds ratio of recurrence in the R group vs. the S group was 4.71. The 5-year survival rate was 85.7% in the S group and 46.7% in the R group, but the difference was not significant (P = .066). The 5-year recurrence-free survival rate was significantly higher in the S group than in the R groups (71% vs. 32%, P = .010). According to Cox's multivariate analysis of recurrence-free survival, the sensitivity test was significantly predictive.
Conclusion: Administration of UFT as postoperative adjuvant therapy to 5-FU-resistant patients had no significant effect on outcome.