The tricky and generally unpredictable nature of cancer is such that it may sometimes make an unwelcome return. But not all is lost. Associate Professor Yap Yoon Sim, a senior consultant in the Division of Medical Oncology at the National Cancer Centre Singapore, explains the treatment options available for patients who suffer a breast cancer relapse. 

Q: What causes breast cancer to relapse and can it be prevented? 

When cancer is diagnosed, there is a risk that some of the cancer cells may have already “escaped” from the breast and spread or metastasised to the lymph nodes, bloodstream or other parts of the body. The hidden metastases may continue to grow and spread over time, leading to a relapse. 

Unfortunately, there are no cancer treatments that can be fully effective against relapse in all patients. However, the risk of a relapse is much lower if the cancer is detected early, and surgery alone may be adequate in such cases. 

Q: What are the treatment options for relapsed stage 4 breast cancer despite five years of hormonal therapy? 

It would depend on a number of factors, including the tumour characteristics and the patient’s general state of health. 

It is important to know the estrogen receptor (ER), progesterone receptor (PR) and human epidermal growth factor receptor 2 (HER2) status of the tumour, ideally with a biopsy of the latest tumour. 

Listed below are three scenarios, each with a standard first-line treatment to follow through. 

  • SCENARIO 1: The tumour is hormone receptor (HR) positive (that is, ER and/or PR positive) and HER2 negative. 
  • THE TREATMENT: Endocrine therapy (also known as anti-hormone therapy) with cyclin dependent kinase (CDK) inhibitors. 

Extensive research has shown that the addition of CDK inhibitors to endocrine therapy can control the cancer more effectively and may also help patients live longer. Chemotherapy is only given if the ER and PR are weakly positive, or if the tumour is very widespread or has stopped responding to the endocrine therapy – with or without CDK inhibitors. 

  • SCENARIO 2: The tumour is HER2 positive. 
  • THE TREATMENT: Chemotherapy with HER2-targeted therapy. 

After the maximal benefit or response has been achieved with chemotherapy, it may be stopped, but the anti-HER2 therapy is usually continued, with endocrine therapy if the tumour is hormone receptor positive. 

  • SCENARIO 3: The tumour is triple negative (i.e. ER, PR and HER2 negative). 
  • THE TREATMENT: Chemotherapy will be the main treatment. 

For triple negative breast cancers that are PD-L1 (programmed death ligand 1) positive, immunotherapy may be added to the chemotherapy. 

Q: What are the factors that determine the type of treatment? 

A patient’s general state of health is important. For example, if the patient is elderly or has other medical problems, some of the treatments mentioned above may not be suitable. Patients should seek advice from their oncologist for the recommended treatment. 

Associate Professor Yap Yoon Sim 
Senior Consultant 
Division of Medical Oncology National Cancer Centre Singapore