I've been diagnosed with early-stage breast cancer. I've heard that a gene expression profiling test might help in planning my treatment. What is it?

Answers from Timothy J. Moynihan, M.D.

Gene expression profiling tests (Oncotype DX, MammaPrint, others) are used in an attempt to determine the right treatment for the right person with early-stage, hormone receptor positive breast cancer. Early-stage breast cancer is cancer that is either confined to the breast or has spread only to nearby lymph nodes, but not to distant parts of the body.

Gene expression profiling is designed to identify people who don't need adjuvant chemotherapy so they can avoid the side effects of unnecessary treatment, and for those who may benefit from adjuvant chemotherapy so they can receive it.

A gene expression profiling test analyzes the patterns of a number of different genes within the your own cancer cells to help predict how likely it is that an early-stage, hormone-sensitive breast cancer will recur after initial treatment. If all of the standard factors that doctors look at to predict the chance of the cancer returning are already very small, then this test is probably not necessary. Nor are these tests very helpful if you have an aggressive cancer in which there is clearly benefit from using chemotherapy. For people who fall between these two categories, a decision needs to be made whether to use chemotherapy, and these tests can be particularly helpful.

The effectiveness of gene expression profiling is still being studied in a number of clinical trials. And while some doctors are using gene expression profiling to plan treatment, others are waiting for the results of these studies.

Discuss with your doctor the pros and cons of gene expression profiling. There are a few gene expression profiling tests currently available. More tests are in development. These tests are not for people with more advanced breast cancer that has spread to distant parts of the body, nor is it helpful if the cancer is not sensitive to hormones, or is HER2 positive. These tests can be expensive (several thousand dollars) and insurance does not always cover the cost of the test.

June 30, 2015 See more Expert Answers