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Chemosensitivity Testing for Breast Cancer Treatment

Know How to Decide on The Most Effective Chemo Treatment for Your Breast Cancer


Updated February 24, 2009

Chemotherapy is such a powerful type of treatment, it is hard to imagine that any type of breast cancer could resist its onslaught. But some breast tumors may resist certain chemotherapy treatments. Rather than prescribe a standard chemotherapy combination without knowing whether or not it would be effective, some oncologists are choosing to test tumor cells in advance of treatment. A chemosensitivity assay can help determine which drugs will most likely shrink the tumor, kill the cancer cells, and give patients the best outcome.

Personalized Treatment for Breast Cancer

Chemotherapy sensitivity and resistance assays (CSRAs) are a relatively new wave of tests done for many types of cancer. A chemosensitivity assay is a laboratory test that is done on a single cell in a test tube (in vitro) or a clump of tumor cells (in vivo), usually taken from a biopsy sample. This test looks at how many cancer cells are killed by a drug, or a combination of drugs, and how many cancer cells resist the treatment. These results are called drug sensitivity and drug resistance.

Once your doctor knows which drugs your cancer will respond to, you can be treated most effectively. This approach ensures that you don't lose any time trying drugs that don't work for you. It also reduces your potential side effects by not subjecting you to powerful toxic drugs that may or may not kill your cancer.

Chemosensitivity Assays Are Not An Escape Hatch

Chemosensitivity testing does not test your potential for side effects from the chemo drugs. The term "chemo sensitive" may sound like this test determines how sick you will feel during treatment. Actually, other factors affect whether or not chemo will cause you some nausea, vomiting, or other side effects. A chemosensitivity assay determines which chemo drugs will make your cancer so 'sick' that it will die.

Testing and Results of a Chemosensitivity Assay

A fresh tissue sample from your tumor will be tested in the lab with several standard single drug doses, and also with standard drug combinations. Your assay report will detail which drugs were used for testing and what doses were used. Each drug will be rated for effectiveness as: sensitive, resistant, intermediate, or active. The lab will make a recommendation for effective treatment, based on the greatest sensitivity score.

Qualifying for A Chemosensitivity Assay

You must meet some qualifications in order for chemosensitivity testing to work for you:
  • currently have a solid or fluid tumor site
  • be willing to have a new biopsy to get a fresh tissue sample for testing
  • have enough strength to undergo chemotherapy
  • have access to a lab or facility that does the chemosensitivity assay

Finances and Testing

Not every type of health insurance will cover a chemosensitivity assay. Medicare most likely will not cover this test. You may have to pay out-of-pocket for lab and consultation fees, which may total as much as $800. Depending on your insurance, you may eventually be reimbursed for a portion of the expenses. Consult your insurance provider before proceeding, and make sure you understand the costs and claim procedures.

Chemosensitivity Assay Test is Still Experimental

New medical tests and procedures have to pass rigorous examination and go through clinical trials before they may be eventually adopted as part of standard practice. Chemosensitivity assays are still considered experimental, in development, and concrete results of independent clinical trials are yet to come. As such, this test is not standard, and it will not be offered to every patient until doctors are convinced of its accuracy and value.

Bottom Line on Chemosensitivity Testing

Before starting treatment, you want to be sure that the journey will be worth the travel. What are the chances that you will survive, and how long will you survive? How can you reduce your risk of recurrence? The point of testing your cancer for chemosensitivity and chemo resistance is to make sure you have the best response rate and greatest chance at beating cancer. Research strongly suggests that when patients receive the most effective treatment, matched to their cancer profile, they survive longer.

Neoadjuvant chemotherapy for breast cancer determined by chemosensitivity assay achieves better tumor response. Gregory I.S.K. Lau, Wings T.Y. Loo and Louis W.C. Chow. Biomedicine & Pharmacotherapy; Volume 61, Issue 9, October 2007, Pages 562-565.

Ellis RJ, Fabian CJ, Kimler BF et al. Factors associated with success of the extreme drug resistance assay in primary breast cancer specimens. Breast Cancer Res Treat 2002;71(2): 95-102

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