Studies conducted by the Eastern U.S. Oncology Collaborative Group have confirmed that sequential administration of endocrine therapy after chemotherapy is superior to combined endocrine therapy at the time of chemotherapy. That is, chemotherapy is recommended first, followed by endocrine therapy at the end.
There is no clear conclusion about the sequence of chemotherapy and radiotherapy. The order of radiotherapy and chemotherapy needs to take into account whether the main risk of breast cancer patients is systemic metastasis or local recurrence. If the risk of systemic metastasis is high, chemotherapy is generally preferred, and if the risk of local recurrence is assessed to be high, radiotherapy is preferred.
Radiotherapy can be given concurrently with endocrine therapy.