Triple-negative breast cancer has a poor prognosis and lacks effective adjuvant treatment. A number of preclinical and clinical trials have shown that bisphosphonates have direct or indirect anti-tumor activity, and early use of bisphosphonate adjuvant therapy can prevent cancer recurrence and metastasis including bone metastasis and greatly improve the prognosis of cancer patients. Bisphosphonates have the advantages of low cost, low toxicity, and strong tolerance and can be used as an auxiliary treatment for triple-negative breast cancer. The preliminary study found that bisphosphonates can be chimeric with erlotinib, an epidermal growth factor receptor tyrosine kinase inhibitor, which can synergistically inhibit the in vitro tumor formation of cancer (such as non-small-cell lung cancer and breast cancer) cells and the growth of transplanted tumors. Therefore, the purpose of this multi-center prospective real-world study was to further investigate the effects of bisphosphonate adjuvant therapy on breast cancer.

Triple-negative breast cancer lacks expression of estrogen receptor, progesterone receptor, and proto-oncogene HER2 as shown by immunohistochemical examination. Its incidence accounts for 15-25% of that of all breast cancer types. This type of breast cancer lacks the opportunity of endocrine therapy and anti-human epidermal growth factor receptor 2 (HER2) therapy. The main currently available treatment is still chemotherapy. Some patients may choose anti-angiogenic therapy. The prognosis of triple-negative breast cancer is worse than that of other types of breast cancer due to fewer treatment options. Bisphosphonates used to treat bone metastasis of breast cancer have been shown to have anti-tumor effects and can be used as an adjuvant treatment for triple-negative breast cancer. The preliminary study found that bisphosphonates can be chimeric with erlotinib, an epidermal growth factor receptor tyrosine kinase inhibitor, which can synergistically inhibit the in vitro tumor formation of cancer (such as non-small-cell lung cancer and breast cancer) cells and the growth of transplanted tumors. The persistence of tumor stem cells is reportedly the root cause of malignant biological behavior of triple-negative breast cancer. Bisphosphonates may synergistically inhibit triple-negative breast cancer (stem) cells with existing molecular targeted drugs.

Although randomized controlled trials can provide highest-level clinical evidence, the test conditions should be strictly controlled, resulting in a small sample size and short follow-up time. However, real-world studies can include patients with multiple diseases and treatment strategies can be adjusted according to patient's needs and clinical conditions. In addition, a variety of interventions can be simultaneously used to accurately meet patient's needs, so that the research evidence is more clinically useful. Therefore, the purpose of this multi-center prospective real-world study was to investigate the significance of use of bisphosphonates as an adjuvant therapy against breast cancer.

Inclusion Criteria:

• developing breast cancer as confirmed by X-ray examination, and cancer tissue was negative for estrogen receptor, progesterone receptor and HER2
• presence of metastatic axillary lymph nodes
• standardized adjuvant therapy
• age over 55 years

Exclusion Criteria:

• pregnant or lactating women
• those allergic to bisphosphonates
• those who are participating in other trials

Patients with triple-negative breast cancer who received treatment in Shengjing Hospital of China Medical University, China.