For some patients with advanced breast cancer, endocrine therapy may be an appropriate option, with often milder adverse effects, easier access, fewer uncomfortable symptoms, and relatively high quality of life compared to chemotherapy.
Which advanced breast cancers are suitable for endocrine therapy?
In general, the following advanced breast cancers are suitable for endocrine therapy.
In general, the following patients with advanced breast cancer are suitable for endocrine therapy:
- Have metastases to bone or soft tissue;
- with visceral metastases but no symptoms and less harmful tumor;
- Tumor progresses slowly and recurrence occurs long before surgery, usually more than 2 years;
- Higher expression levels of hormone receptors.
The above patients are more likely to benefit from endocrine therapy. In addition, early pathologic testing or immunohistochemical testing levels may affect hormone receptor results, and the receptor expression status of metastases may be different from the primary site in the breast. Based on these factors, physicians sometimes try endocrine therapy for some slowly progressing, hormone receptor-unknown or hormone-receptor-negative breast cancers.
Endocrine therapy for advanced breast cancer, what drugs are available?
- Ovarian function inhibitors, including goserelin and leuprolide. There are many means of ovarian function suppression (OFS), including surgery, radiation therapy, and pharmacotherapy. Surgery and radiotherapy are gradually replaced by ovarian suppression drugs due to factors such as irreversibility, controllability check, and more side effects. However, surgery for OFS is also an appropriate option for patients who are financially disadvantaged, or approaching menopause.
- Third-generation aromatase inhibitors, including nonsteroidal (anastrozole, letrozole) and steroidal (exemestane) drugs. Inhibit non-ovarian sources of estrogen production by inhibiting aromatase to achieve control of tumor progression.
- Drugs that act on the estrogen receptor, including estrogen receptor downregulators (fulvestrant) and estrogen receptor modulators (tamoxifen and toremifene). By downregulating or competitively binding to estrogen receptors, they block the interaction between estrogen and estrogen receptors, thereby inhibiting the growth of tumor cells.
What drugs to use and how to choose?
For those who decide to use endocrine therapy, physicians consider primarily menstrual status and prior endocrine drug use when selecting medications.
For postmenopausal patients, third-generation aromatase inhibitors, estrogen receptor downregulators, estrogen receptor modulators, and progesterone analogs may be considered. In premenopausal patients, OFS is required before consideration of these agents.
Depending on the type and timeframe of prior endocrine use, physicians usually do not prefer the same type of endocrine medication as previously used. For postmenopausal patients who have not used endocrine medications, or who have relapsed after a longer period of time, fulvestrant, third-generation aromatase inhibitors, and tamoxifen may be chosen. Those who have received adjuvant therapy with tamoxifen may choose fulvestrant, third-generation aromatase inhibitors. For postmenopausal patients, third-generation aromatase inhibitors have better disease control than tamoxifen, and the efficacy is similar between anastrozole, letrozole, and exemestane.
Fulvestrant, everolimus in combination with exemestane, CDK4/6 inhibitors in combination with endocrine therapy, or mTOR inhibitors in combination with endocrine therapy may be considered if previous treatment with nonsteroidal aromatase inhibitors has failed.
If tumor progression after three consecutive lines of endocrine therapy is usually indicative of resistance to endocrine therapy, physicians may consider switching to chemotherapy or recommend enrollment in a clinical trial.
Regular review is important during treatment
During endocrine therapy, your doctor will recommend review 1 every 2 to 3 months to assess the efficacy, and if you assess complete remission (CR, where the lesion is seen to disappear completely and persist for a period of time), partial remission (PR, where the lesion is seen to decrease somewhat and persist for a period of time), and stable disease (SD, where the lesion remains stable and only slightly enlarges or shrinks), you will usually continue to maintain endocrine therapy, and if the tumor progresses, the physician will decide to change to other mechanisms of endocrine therapy drugs or to switch to other treatments such as chemotherapy, depending on the disease.
Even patients with advanced breast cancer may benefit from endocrine therapy, and following treatment principles and doctor’s advice is key to improving the condition of patients with advanced breast cancer.