The characteristics of a breast cancer -- including hormone receptor status and HER2 status -- can change over time. These changes may happen because the cancer cells change themselves or because treatment changes the cells. A cancer's characteristics determine which treatments will offer the most benefit.
A Swedish study has found that the hormone receptor status and HER2 status of a breast cancer can change after it’s diagnosed. These changes were seen after some early-stage breast cancer came back (recurred) as either locally advanced or metastatic breast cancer. Changes in a cancer’s hormone receptor status and HER2 status were also seen in some advanced-stage cancers as they grew.
Locally advanced breast cancer is advanced-stage cancer that has spread to the chest wall below or the skin above the breast. Metastatic breast cancer is advanced-stage cancer that has spread to other parts of the body away from the breast, such as the bones or liver.
The results were published online June 17, 2012 in the Journal of Clinical Oncology. Read the abstract of “Clinically Used Breast Cancer Markers Such as Estrogen Receptor, Progesterone Receptor, and Human Epidermal Growth Factor Receptor 2 Are Unstable Throughout Tumor Progression.”
Right now, doctors don't typically do a new biopsy when previously treated breast cancer comes back as advanced-stage disease or when advanced-stage breast cancer grows over time. Treatment decisions are usually still based on the hormone receptor and HER2 status from the original breast cancer biopsy.
This study found that in some cases a cancer's characteristics do change over time – and the changes could affect treatment. So doing a biopsy on recurrent, advanced-stage cancer to see if the hormone receptor and HER2 status has changed may make sense.
The researchers looked at biopsy results from more than 1,000 women who were diagnosed with early-stage breast cancer and received treatment. All the women then had one or more additional biopsies when the cancer came back or grew. The researchers compared the biopsy results from the original breast cancer to the additional biopsy results:
- about 33% of the later biopsies showed hormone receptor status had changed
- about 15% of the later biopsies showed HER2 status had changed
In some cases the hormone receptor status or HER2 status changed from positive to negative. In other cases the hormone receptor status or HER2 status changed from negative to positive. These changes would definitely affect treatment choices.
- If a cancer changed from HER2-negative to HER2-positive but a woman and her doctor didn’t know this, they might not consider treating the cancer with a medicine that targets HER2-positive cancers, such as Herceptin (chemical name: trastuzumab), even though the cancer may now respond to that medicine.
- If a cancer changed from hormone-receptor-negative to hormone-receptor-positive but a woman and her doctor didn’t know this, they might not consider treating the cancer with hormonal therapy, even though the cancer may now respond to those types of medicines.
Doing a biopsy of breast cancer that has spread to soft tissue such as the liver usually can be done easily and safely. Breast cancer that has spread to the bones is harder to biopsy. Earlier research suggests that breast cancer that has spread to the bones is much less likely to change characteristics over time compared to breast cancer that has spread to soft tissue. So a new biopsy of breast cancer that has spread to the bones may not be necessary.
If you've been diagnosed with recurrent advanced-stage breast cancer, especially breast cancer that has spread to soft tissue such as the liver, you may want to talk to your doctor about this study and ask if doing a new biopsy of the cancer makes sense.
You can learn more about breast cancer characteristics on the Breastcancer.org Getting Your Pathology Report pages.