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?

Answer From Sandhya Pruthi, M.D.

Gene expression profiling tests (Oncotype DX, MammaPrint, others) analyze a number of different genes within your cancer cells to predict your risk of cancer recurrence.

The results of gene expression profiling tests help doctors determine who may benefit from additional (adjuvant) treatment after surgery. For women with early-stage breast cancer that is sensitive to hormones, gene expression profiling tests are used to determine whether they are likely to benefit from adjuvant chemotherapy.

If all of the standard factors that doctors use to predict the chance of your cancer returning show that your risk is very small, then gene expression profiling tests probably aren't necessary. Nor are these tests very helpful if you have an aggressive cancer in which there is clearly benefit from using chemotherapy. For cancers that fall between these two categories, a decision needs to be made about whether to use chemotherapy, and gene expression profiling can be particularly helpful.

Several gene expression profiling tests exist, and many are being studied in clinical trials. Doctors are still determining how best to use these tests and interpret the results.

One recent study found that chemotherapy might not be helpful for women with gene expression profiling test results that indicate an intermediate risk of recurrence. In the study, some of the women received hormone therapy and chemotherapy after surgery and some women received hormone therapy only.

Both groups had similar survival rates, which indicated that the chemotherapy was unnecessary for most of the women. Chemotherapy showed some benefit for women who were 50 or younger and had gene profiling test scores in the upper end of the intermediate range. The results of this study apply only to women who have intermediate scores on the Oncotype DX test and tumors that are hormone sensitive and HER2 negative and haven't spread to the lymph nodes.

Talk with your doctor about the pros and cons of gene expression profiling. These tests can be expensive, and insurance doesn't always cover the cost.

June 29, 2018 See more Expert Answers