Breast cancer is currently the most common form of cancer in women, regardless of race or ethnicity. Overall, breast cancer ranks as the second leading cause of cancer-related deaths among women.

Breast cancer mortality trends have declined significantly during the past decade, largely due to public awareness campaigns that focus on early detection and prevention. However, early screening can also result in some patients being overtreated.

Screening tests, such as mammography and MRI, can detect very low-risk, non-life-threatening tumors, and this can sometimes lead to unnecessarily aggressive treatment. The problem is often exacerbated because the cancer can recur within five years, and because there had been no tools able to accurately predict which patients were the likeliest to survive over that period.

But this is no longer the case. Researchers have found that a molecular test can help to predict which breast cancer patients will have the lowest risk of death. A patient of our practice underwent this testing, and asked me to discuss it.

This test is called MammaPrint, and other tests which basically look at the same thing have been around for many years, initially approved by the United States Food and Drug Administration (FDA) in 2007. The tests have been proven to provide insight into which tumors are aggressive, and those that are not.

MammaPrint is a 70-gene signature test that is widely used to determine which patients do or do not need chemotherapy after surgery.

In a study published in 2016, this test indicated that almost half of the breast cancer patients that were considered “early stage,” but who had all the traditional signs of being at a high risk of recurrence, could, in fact, do without chemotherapy. This evaluation was based on the biological composition of the tumors.

This research used this test to evaluate the risk of breast cancer recurrence over a period of 20 years after being diagnosed. To do so, they examined patients from the Stockholm Breast Cancer Study group, all of whom had been clinically followed for decades as part of a clinical trial for the tumor-suppressing drug tamoxifen.

The trial included 1,780 patients whose breast cancer had not spread to their lymph nodes. All the women had had a mastectomy or a lumpectomy and undergone radiation treatment. The researchers went back and used the tissue from the patient’s original surgery to calculate the MammaPrint risk scoring for 652 women. The 70-gene signature test identified 42% of the patients as being at high risk of recurrence, and 58% as being at low risk.

When reviewing the data, researchers found that 95% of those deemed low risk survived for five years, but also that some of them died later from breast cancer.

However, the test also categorized 15% of the patients as “ultralow risk.” These patients had “excellent long-term survival,” regardless of whether or not they took tamoxifen. The 20-year breast cancer-specific survival rate among ultralow-risk patients was 97% among those who took tamoxifen.

This test and others like it are an important step forward for personalizing care for women with breast cancer. We can now test small node-negative breast cancers, and if they are in the ultralow-risk category, we can tell women that they are highly unlikely to die of their cancers, and do not need aggressive treatment.

Dr. C. Joseph Bennett Jr. is a board-certified radiation oncologist. If you have any suggestions for topics, or have any questions, contact him at 522 N. Lecanto Highway, Lecanto, FL 34461, or email cjbennett@rboi.com.

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