Phase II study of oral S-1 monotherapy in metastatic colorectal cancer after failure of both irinotecan and oxaliplatin-containing regimen

Abstract

3597 Background: There has been a considerable increase in the number of patients (pts) with mCRC pretreated with both irinotecan and oxaliplatin. Little is known about third-line therapy in this group of pts. We conducted a phase II trial of oral S-1 in pts with advanced colorectal cancer who failed on both irinotecan and oxaliplatin. Methods: This phase II study was designed to evaluate the activity and toxicity of S-1 monotherapy in 31 advanced colorectal cancer pts (P0 = 3%, P1 = 15%; α = 0.05, power = 80%, drop-out rate 10 %). S-1 was administered orally twice daily, 70 mg/m2/day for 14 days followed by 1-week rest. Eligibility criteria included ECOG 0–2; measurable lesion; adequate organ functions; signed informed consent. Results: As of 1st September 2005, 21 pts were enrolled. Median age of all pts 55 years. There were 10 male and 11 females. Thirteen of 21 patients were treated with oxaliplatin-containing regimens as a first-line therapy for metastatic diseases. The median number of treatments was 3 courses (range, 1–10). The relative dose intensity was 1.0 (0.83 - 1.0) with a median dose of120 mg (100 -140 mg). Nineteen out of 21 patients were evaluable. The confirmed response rate was 21.1% (4/19, 1 CR, 3 PR). The median PFS was 11 weeks, and median OS was not reached. The most frequent adverse reaction was skin pigmentation (47.6%). Grade 3 toxicities was skin pigmentation in 1 patients (4.8%), neutropenia in 1 (4.8%), and anemia in 1 (4.8%), respectively. Conclusion: This results shows that S-1 produces a promising response rate with an acceptable safety profile in refractory, mCRC. S-1 has the potential to become a valuable option as a third-line salvage regimen in irinotecan and oxaliplatin pretreated mCRC pts. Clinical trial of combination therapy with S-1 will be warranted. No significant financial relationships to disclose.