Breast cancer (BC) is one of most prevalent malignant tumors in the world. According to the 2020 edition of the global cancer statistics report, the incidence rate of BC has overtaken lung cancer to become the most commonly diagnosed cancer.
In the past three decades, survival of patients with primary BC have been notably improved, mainly due to early detection of the disease and advances in adjuvant treatments such as endocrine therapy, chemotherapy, and anti-HER2 therapy. Patients with HR-positive and HER2-negative primary BC account for approximately 70% of all cases of early breast cancer. Endocrine therapy is the core treatment for this subtype of BC. Tamoxifen, aromatase inhibitor or their sequential administration can reduce the recurrence and mortality of this BC subtype.
The results of TEXT/SOFT study showed that, compared with the traditional 5-year tamoxifen treatment, tamoxifen + OFS or aromatase inhibitor + OFS can further improve the survival of HR+/HER2- breast cancer patients. However, for premenopausal BC patients with HR+/HER2-, only 82.5% (tamoxifen plus OFS) and 85.7% (aromatase inhibitor plus OFS) of 5-year DFS were achieved. For postmenopausal BC patients, the 5-year DFS was only about 84% with aromatase inhibitors. Therefore, the survival of HR+/ HER2- BC patients needs to be further improved.
Metronomic chemotherapy refers to the use of the minimum effective dose of chemotherapy drugs for long-term, uninterrupted administration to achieve anti-tumor effect. Metronomic chemotherapy has gradually been verified in clinical practice in the past 20 years. In 2020, SYSUCC-001 study has confirmed that capecitabine (650 mg/ m2 bid, for 1 years) can reduce the risk of 5-year DFS events by 36% in TNBC patients in addition to standard treatment. Besides, POTENT study has confirmed that the combination of endocrine therapy and S-1 (for one year) can further reduce the risk of iDFS by 37% in HR+/HER2- BC patients who have completed the standard treatment.
Compared with capecitabine, S-1 has no indication for BC and it is not in the recommendation for BC treatment in the guidelines. Therefore, the investigators conduct this study to explore whether adjuvant Capecitabine metronomic chemotherapy for one year can further improve the survival of BC patients with HR+/ HER2- in addition to standard treatment.