How does hormone receptor status affect patient response to trastuzumab therapy in metastatic breast cancer

This study investigated the clinical factors that influence patient response to trastuzumab (Herceptin) therapy in human epidermal growth factor receptor 2 positive (HER2+) metastatic breast cancer (MBC). Hormone receptor (HR) status was found to be a possible predictor of a strong response to trastuzumab-based therapy.

Trastuzumab is the main treatment option for HER2+ breast cancer. However, patients with HER2+ breast cancer may also have other factors driving cancer growth, such as hormone receptors. In HR positive (HR+) breast cancer, the hormones estrogen or progesterone can increase cancer growth. Patients who are HER2+/HR+ tend to have lower rates of remission (no sign of disease) than patients who are HER2+/HR negative (HR-). 

Only 10% of HER2+ MBC patients experience a lasting response of more than 3 years. The role of HR status in HER2+ treatment response is not well known.

This study included 153 women with HER2+ MBC who were treated with trastuzumab and either paclitaxel (Taxol) or docetaxel (Taxotere) as their primary treatment. The patient’s HR status and metastases were reviewed. Average follow-up time was 28 months with an average age of 52 years. Progression-free survival (PFS; time from treatment until disease progression) and overall survival (OS; time from treatment until death from any cause) were measured.

HR- patients showed a longer average PFS (19 months), compared to HR+ patients (9 months). The OS of HR- patients was 37 months. HR+ patients had an OS of 47 months.

Bone metastases were also associated with a longer PFS (15 months) and OS (75 months) than metastases to internal organs which showed a PFS of 11 months and OS of 34 months.

The study concluded that HR status is a possible predictor of outcome in patients with HER2+ MBC who receive trastuzumab-based therapy. Sites of metastases were found to independently influence treatment response.

This study relied on the use of patient records and used a small sample size. This means some selection bias may be present in the results. A larger study is needed to confirm the results.

Discuss with your doctor how HR status may affect your treatment.