Phase II multi-center clinical study on using S-1 to treat advanced breast cancer after resistance to anthracycline and taxane drugs in Chinese patients.

backgroundTreatment for metastatic breast cancer (MBC) in patients who have relapsed from anthracycline and taxane is difficult. S-1, an oral 5-FU derivative, has demonstrated a potential antitumor effect in patients with MBC. Thus, we evaluated the efficacy and safety of S-1 as second-line chemotherapy MBC patients in a phase II trial.

methodsThe study was conducted at seven centers in China and enrolled MBC patients who had previously relapsed from one chemotherapy regimen. The median progression-free survival (PFS) was the primary end point. The treatment schedule involved the administration of S-1 at a standard dose based on the body surface area (BSA) in 28-day cycles with consecutive administration followed by a 14-day rest, as follows: 40 mg twice daily if BSA < 1.25 m(2); 50 mg twice daily if 1.25 m(2) ≤ BSA ≥ 1.5 m(2); and 60 mg twice daily if BSA > 1.5 m(2).

resultsThirty-three patients were included in the analysis. S-1 demonstrated moderate efficacy with a PFS of 3.3 months, a response rate of 33.3%, and a disease control rate of 72.7%. The treatment was well-tolerated with mild-to-moderate toxicity. Grade 3 adverse events (AEs) occurred in 4 patients (2 with hyperbilirubinemia, 1 with anorexia, and 1 with vomiting). Grade 4 AEs were not observed.

conclusionS-1 demonstrated encouraging efficacy and safety in a prospective trial as second-line treatment in MBC patients. All AEs were manageable; however, bilirubin monitoring is recommended during treatment.