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 are used to decide which treatments will offer the most benefit.
In a study, researchers found that 12.1% of metastatic breast cancers that were biopsied had different characteristics than the original cancer that was diagnosed in the breast. All the cancers were metastatic because they had spread from the breast area to the liver. These results were presented at the 2010 American Society of Clinical Oncology (ASCO) annual meeting.
Right now, doctors don't biopsy every metastatic breast cancer that is diagnosed. In many cases, the characteristics of the metastatic cancer are the same as the original breast cancer. Still, this research suggests that in some cases a cancer's characteristics can change if the cancer comes back in another place in the body. So doing a biopsy on metastatic cancer may make sense in some cases, especially for breast cancer that has spread to the liver.
In this study, the researchers looked at biopsy results from 255 women who had been diagnosed with breast cancer and then later diagnosed with metastatic breast cancer in the liver. They compared the biopsy results from the original breast cancer to the biopsy results from the metastatic breast cancer in the liver. If a cancer characteristic was different in the metastatic biopsy compared to the original biopsy, it was called discordant. Discordant characteristics meant that the cancer cells had changed over time.
Overall, 13.9% of the cancers had a change in HER2 status:
- 31.5% of HER2-positive original breast cancers were HER2-negative based on the metastatic cancer biopsies; this means that in about one-third of the cases, basing treatment decisions on the original HER2-positive status likely led to treatment with a medicine that targets HER2-positive cancers even though the cancer probably wouldn't have responded to the medicine because it was HER2-negative
- 5.9% of HER2-negative original breast cancers were HER2-positive based on the metastatic cancer biopsies; this means that in about 6% of the cases, basing treatment decisions on the original HER2-negative status likely meant that these women weren't treated with a medicine that targets HER2-positive cancers even though the cancer probably would have responded to the medicine
Overall, 14.5% of the cancers had a change in hormone-receptor status:
- 25.9% of estrogen-receptor-negative original breast cancers were estrogen-receptor-positive based on the metastatic cancer biopsies; this means that in about one-quarter of the cases, basing treatment decisions on the original estrogen-receptor-negative status likely meant that these women weren't treated with hormonal therapy (an aromatase inhibitor, tamoxifen, or Faslodex) even though the cancer probably would have responded to the medicine
- 11.2% of estrogen-receptor-positive original breast cancers were estrogen-receptor-negative based on the metastatic cancer biopsies; this means that in about 11% of the cases, basing treatment decisions on the original estrogen-receptor-positive status likely led to hormonal therapy treatment even though the cancer probably wouldn't have responded to the medicine
A biopsy on breast cancer that has spread to the liver usually can be done easily and safely. This study suggests that the information from a metastatic cancer biopsy could help doctors make more informed treatment decisions based on the most up-to-date cancer characteristics. Based on this and other studies, many doctors feel that when breast cancer spreads to soft tissue such as the liver, another biopsy should be done on the metastatic cancer, provided it's safe to do so. Information from the metastatic biopsy can help make sure that treatment decisions are based on the actual cancer characteristics.
Breast cancer that has spread to the bones (as opposed to soft tissue such as the liver) is harder to biopsy. Still, an earlier study by the same researchers found that metastatic cancer had the same characteristics as the original cancer about 95% of the time. This suggests that breast cancer that has spread to bones is less likely to change its characteristics over time so probably doesn't have to be biopsied.
If you've been diagnosed with metastatic 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 biopsy on the metastatic cancer makes sense.
You can learn more about breast cancer characteristics on the Breastcancer.org Your Breast Cancer Diagnosis pages.
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