Research Suggests How Metastatic Cancer Becomes Resistant to Chemotherapy

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Metastatic breast cancer is breast cancer that has spread to parts of the body away from the breast, such as the bones or liver.

Chemotherapy medicines prevent cancer cells from growing and spreading by destroying the cells or stopping them from dividing. Chemotherapy is used to treat metastatic breast cancer by destroying or damaging the cancer cells as much as possible. Chemotherapy weakens and destroys cancer cells at the original tumor site AND throughout the body.

Most normal cells grow and divide in a precise, orderly way. Still, some normal cells do divide quickly, including cells in hair follicles, nails, the mouth, digestive tract, and bone marrow (bone marrow makes blood cells). Chemotherapy also can unintentionally harm these other types of rapidly dividing cells.

In some cases, a cancer stops responding to a particular chemotherapy medicine or combination of medicines. When this happens, doctors say the cancer is resistant to that chemotherapy.

A very early study on breast, ovarian, and prostate cancer cells in petri dishes in the lab has found that a type of cell called a fibroblast also is damaged by the chemotherapy medicines cisplatin (brand name: Platinol-AQ), Blenoxane (chemical name: bleomycin), and Novantrone (chemical name: mitoxantrone). Normally fibroblasts help wounds heal and play a role in collagen production. When fibroblasts are damaged by chemotherapy, they make a protein called WNT16B that may help metastatic cancer cells become resistant to chemotherapy and grow.

The research was published online on Aug. 5, 2012 by the journal Nature Medicine. Read the abstract of “Treatment-induced damage to the tumor microenvironment promotes prostate cancer therapy resistance through WNT16B."

It’s very important to know that this research is VERY early. What happens to single cells in a petri dish in the lab may not happen in the environment of the human body. Much more research needs to be done and any changes in treatment won’t happen for 10 or 15 years.

It’s also very important know that the three chemotherapy medicines looked at in this study – cisplatin, Blenoxane, and Novantrone – are not commonly used to treat breast cancer. They are mainly used to treat prostate cancer or ovarian cancer.

Finally, it’s also important to know that while the researchers looked at breast and ovarian cancer cells in the study, much of the research was focused on prostate cancer. It’s also not clear if the fibroblasts near metastatic breast cancer cells produce WNT16B in response to all types of chemotherapy of just certain medicines. Nor is it clear if the personality of the breast cancer -- HER2 status, hormone receptor status -- affects how the fibroblasts respond to chemotherapy.

Again, much more research needs to be done before any changes to treatment standards are made.

If you’ve been diagnosed with metastatic breast cancer, you and your doctor may be considering a number of treatment options, including chemotherapy. Research has shown that newer chemotherapy medicines such as:

  • Taxol (chemical name: paclitaxel)
  • Abraxane (chemical name: albumin-bound or nab-paclitaxel)
  • Taxotere (chemical name: docetaxel)
  • Adriamycin (chemical name: doxorubicin)
  • Ellence (chemical name: epirubicin)

are helping women diagnosed with metastatic breast cancer live longer.

Keep in mind that each person’s treatment plan will be different. What works for you may not work for someone else and what works for someone else may not work for you. Still, there are some general guidelines that doctors follow when using chemotherapy to treat metastatic breast cancer:

  • If you've had chemotherapy before, your doctor may recommend using only one chemotherapy medicine at a time to treat metastatic disease. This way you get benefits with fewer possible side effects.
  • In general, most chemotherapy medicines can be used until side effects become a problem or the medicine stops being effective.
  • Some chemotherapy medicines seem to work better against cancer tumors when used in combination. So your doctor may recommend a combination of medicines for you because research has shown that combining treatments has contributed to a better overall prognosis for some metastatic cancers.
  • If you've had chemotherapy before and the cancer came back or didn't respond, your doctor will likely recommend a different combination of medicines. There are many chemotherapy medicines and if one medicine or combination of medicines doesn't seem to be working, there is almost always something else you can try.

For more information, including chemotherapy medicines and combinations, visit the Breastcancer.org Chemotherapy pages.

Stay tuned to Breastcancer.org Research News for the latest information on breast cancer treatments and their effectiveness.

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