Neoadjuvant chemotherapy remains an inseparable part of systemic therapy for hormone receptor positive (HR+) advanced breast cancer. However, efficacy of neoadjuvant chemotherapy in this subtype of patients is inferior to its hormone receptor negative counterpart. Several preclinical and clinical studies have suggested that it was growth rate rather than hormone receptor status that determined sensitivity to chemotherapy. In addition, estrogen was proved to recruit more HR+ breast cancer cells into actively dividing phase according to various studies. For premenopausal females, sexual hormone like estradiol fluctuates with menstrual cycle. When menstruation occurs, women have the lowest level of estradiol, which is resemble to pharmaceutical effect of endocrine therapy. If chemotherapy is given to females during menstruation, it's almost equal to concurrent use of chemotherapy and endocrine therapy, which is not recommended by guideline. Accordingly, chemotherapy would attain best efficacy applied at the peak of estradiol, because more tumor cells being in actively dividing phase recruited by comparatively high level of estradiol would help cytotoxic agents function better given that majority of chemotherapeutic drugs are cellular phase dependent. We name this rhythmic mode of chemotherapy for premenopausal HR+breast cancer females, giving chemotherapy to patients when estradiol rises and avoiding prescription at menstruation, tidal chemotherapy. It's postulated that tidal chemotherapy would improve efficacy of neoadjuvant chemotherapy for premenopausal HR+breast cancer females, achieve more pathologic complete response and in the long run improve prognosis.
Keywords: Breast cancer; Hormone receptor; Neoadjuvant chemotherapy; Tidal chemotherapy.
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