It seems difficult to find the silver lining when you learn that your hormone receptor-positive breast cancer has spread. However, it is important to know that it may be treated and kept under control. 

Dr Elaine Lim, a senior consultant in the Division of Medical Oncology at the National Cancer Centre Singapore, explains metastatic breast cancer, the hormonal status of breast cancer and its treatment options. 

Q: What does it mean to have metastatic breast cancer? 

In metastatic breast cancer, the disease has spread beyond its original location, for example, to the bones, lungs, liver or other parts of the body. Given this situation, the disease cannot be cured, but there is a good chance of keeping the cancer under control, such that symptoms (if any) are improved or prevented.

Q: What does ER/PR+ HER2- metastatic breast cancer mean?

Estrogen receptor (ER) and progesterone receptor (PR) are female sex hormone receptors, and may reside in breast cells. 

Human epidermal growth factor receptor type 2 (HER2) is a protein receptor that may be present on the surface of breast cells. 

If ER, PR or HER2 are stimulated, breast cells behave like cancer cells. The presence or absence of ER, PR and HER2 are routinely tested for in breast biopsies. 

In the case of ER/PR+ HER2- metastatic breast cancer, it means the patient’s tissue sample has been tested positive for ER and/or PR and negative for HER2. 

Q: How is ER/PR+ HER2- metastatic breast cancer treated and what are the side effects?

The mainstay of treatment would be hormonal therapy. Advances in breast cancer treatment have led to the incorporation of cyclin-dependent kinases 4 and 6(CDK4/6) inhibitors in hormonal therapy as part of first-line treatment. 

These medicines have been clinically proven to be effective in inducing tumour response and improving survival, when used in combination with hormonal therapy. 

The side effects are generally better tolerated than that of chemotherapy. There is no hair loss, severe nausea and vomiting, numbness and tingling in the finger or toe tips, nor other severe adverse effects on organ function. 

While there may be a lower white cell count (an indication of immune system status), it is usually not associated with fever. For chemotherapy patients, a fever with a low white cell count would mean they need to be hospitalised for tests, monitoring and antibiotics.

Q: What are the factors that will influence the choice of hormonal therapy?

Some factors include whether metastases are present at initial diagnosis or relapse, and whether the patient is pre- or post-menopausal. 

Aromatase inhibitors are orally administered hormonal therapy. For pre-menopausal women, they are given in conjunction with ovarian suppression, which is induced with monthly or quarterly injections. 

Fulvestrant is another hormonal therapy that may be used in combination with a CDK4/6 inhibitor, depending on when metastases are diagnosed.

Dr Elaine Lim 
Senior Consultant 
Division of Medical Oncology 
National Cancer Centre Singapore