Understanding Chemosensitivity Testing

The Basics on This Experimental Type of Testing

test tubes in lab
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Chemotherapy is a powerful type of treatment, it's hard to imagine that any type of breast cancer could resist its onslaught — but some breast tumors do. By testing the tumor cells ahead of time through a test called chemosensitivty and resistance assay, or CRSA, an oncologist can predict which chemotherapy will be most effective.  

What is a Chemosensitivity Testing?

Chemotherapy sensitivity and resistance assays (CSRAs) are a relatively new wave of tests done for many types of cancer.

They are in vitro laboratory tests — meaning analyzed in a test tube — of cells taken from a tumor to help predict whether the tumor is sensitive or resistant to a certain chemotherapy drug. 

The purpose of these tests is to determine which chemotherapy a person's cancer will respond to. CRSAs also help a person avoid the potentially toxic side effects of a chemotherapy that isn't going to kill their tumor cells anyway.

How Much Do CSRAs Cost?

Not every type of health insurance will cover chemotherapy sensitivity and resistance tests.  You may have to pay out-of-pocket for lab and consultation fees. 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 Testing 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 — there are no large, randomized clinical studies to support its benefit. Also, there is no standard protocol for how CRSAs are performed. As such, this test is not a typical practice.

In 2011, the American Society of Clinical Oncology reviewed the scientific data on chemosensitivity testing and concluded that while this type of testing is potentially important, it should be limited to patients who are participating in clinical trials.

The society recommended that oncologists should choose chemotherapies for their patients based on published clinical trials, a person's health status, and their treatment preferences. 

At this time, it seems that chemosensitivity testing is mostly limited to a small subset of people.

What Should I Do?

If you are anticipating chemotherapy, the best thing you can do is to speak with your oncologist about your options, potential side effects, and treatment expectations. Be proactive in your health.


Burstein et al. American Society of Clinical Oncology clinical practice guideline update on the use of chemotherapy sensitivity and resistance assays. J Clin Oncol. 2011 Aug 20;29(24):3328-30.

Ellis RJ 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.

Jenks S. Chemosensitivity assays: still eyeing the clinic. J Natl Cancer Inst. 2012 Dec 5;104(23):1775-7.

Lau GI, Loo WT, & Chow LW. Neoadjuvant chemotherapy for breast cancer determined by chemosensitivity assay achieves better tumor response. Biomed Pharmacother. 2007 Oct;61(9):562-5.

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