Key clinical point: For patients with hormone receptor–positive, HER2-negative postoperative breast cancer, adding S-1 to standard endocrine therapy may reduce risk of disease recurrence.

Major finding: The 5-year invasive disease-free survival was 86.9% among patients who received endocrine therapy plus S-1, compared with 81.6% for patients who received endocrine therapy alone (P less than .001).

Study details: The open-label phase 3 POTENT trial, conducted in Japan, involved 1,932 patients with hormone receptor–positive, HER2-negative postoperative breast cancer.

Disclosures: The study was funded by the Comprehensive Support Project for Oncology Research of the Public Health Research Foundation and Taiho Pharmaceutical. The investigators reported additional relationships with Bristol-Myers Squibb, Daiichi Sankyo, Genomic Health, and others.