Breast Cancer Recurrence Risk and Genomic Testing

The most important comment is that there is no sure way to predict an individual woman’s (or man’s) risk of a breast cancer recurrence. There are lots of statistics related to the specifics of the diagnosis and the pathology, but statistics always refer to a large group of people, not to one person. Genomic testing is completely individualized and refers to tests that look at all of someone’s genes, not a specific gene or set of genes. Genomic testing is a way of looking broadly for potentially harmful genetic changes anywhere in someone’s full genetic code.

Increasingly genomic tests are being used to make treatment decisions, to help doctors and patients decide when chemotherapy is important and when it is likely not needed. Note that there is always an emotional piece to this decision, so that just knowing the numbers will not necessarily dictate the right answer.

The best known test is the Oncotype DX for women with a new diagnosis of ER and/or PR positive, HER2 negative breast cancer that has not spread to the lymph nodes. The test looks at a total of 21 genes in a tumor sample and results in a recurrence score that indicates the risk of a recurrence in the next ten years. Oncologists may use the results of this test to help guide a decision about chemotherapy. The recommendations may vary with the patient’s age and other factors of her medical history or other medical problems. There are three broad categories of the score: low, intermediate, and high risk. Those women whose score is in the middle group may have the most difficult decision to make. The likely benefit from chemotherapy may be less, and chemo always brings some risks and unpleasant months.

When my second breast cancer was diagnosed in 2005, the Oncotype DX was a new test. My results came back in the intermediate range, and I was faced with this very decision. Given my long years in Cancer World, it wasn’t such a tough choice. First, I had been through chemo before so that I knew I could do it. Second, I had witnessed far too many women die from breast cancer, and I wanted to do everything possible to stay well. I do understand that we each bring our own history and perspective to medical choices, and there is no single right answer for everyone.

A newer test is the MammaPrint that is also for women in this group plus those who have up to three positive lymph nodes. It looks at a total of 70 genes to help women at a higher risk of recurrence make a decision, with their doctors, about adding chemotherapy to their treatment.

Other less-commonly used genomic tests include the Breast Cancer Index, PAM50, EndoPredict, and uPA/PAI. These tests are also intended for women with ER and/or PR positive, HER2 negative breast cancers.

Note that none of these tests are useful for women with HER2 positive or triple negative breast cancers. Almost always, a diagnosis of one of these cancers will come with a recommendation of chemotherapy.

It is helpful to know that these tests exist and may provide additional information to aid in decision making. A result may support a newly diagnosed woman’s instincts about chemotherapy, but it may also contradict them. It is important to think carefully about the facts and to remember that no one has a crystal ball or certainty about the future. My standard piece of advice to women who are struggling with the chemo decision, with or without the assistance of genomic testing results, is to think about a choice that will help them sleep better now as well as three or five years from now. Another sometimes helpful perspective is this: If you can identify the worst possible outcome, you can probably make a choice to avoid that’s happening.