A similar proportion of patients required dose reductions (12% vs 11%, respectively) or discontinued treatment (7% each group) due to adverse events with S-1 or taxanes.

Dr Takashima and colleagues used the 30-item, patient-assessed EORTC Quality of Life Questionnaire (QLQ-C30) to measure health-related quality of life. Treatment with S-1 vs taxanes led to significantly (P = .039) better global health status and significantly higher scores in all 5 functional domains (physical, role, emotional, cognitive, and social).

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Most of the symptom domains (eg, fatigue, nausea and vomiting, appetite loss) showed no difference between S-1 and taxanes, although patients treated with S-1 had better scores for pain (P = .039) and financial difficulties (P = .0023). Furthermore, at 36 months, scores on the EQ-5D utility measures were significantly higher with S-1 (P = .033).

The authors wrote that, “the goals of treatment of mBC are prolonging survival and improving quality of life.”1 Their study demonstrated that orally administered S-1 met those goals as well as or better than a current standard of care, taxanes.

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The results provided “much-needed evidence” for the benefit of S-1, “which has been used in clinical practice on the basis of consensus among medical practitioners without sufficient evidence,” concluded the authors.1

A second study is underway to compare S-1 with anthracycline-based regimens, another standard cytotoxic chemotherapy in the same type of patients.


  1. Takashima T, Mukai H, Hara F, et al. Taxanes versus S-1 as the first-line chemotherapy for metastatic breast cancer (SELECT BC): an open-label, non-inferiority, randomised phase 3 trial [published online ahead of print November 23, 2015]. Lancet. doi: 10.1016/S1470-2045(15)00411-8