This is personal: Less chemotherapy for breast cancer
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A close relative was diagnosed of invasive breast cancer five years ago. After surgery she received chemotherapy and did well, today she is in remission. Would she still be in remission without chemotherapy?

In patients with breast cancer, oncologists are always confronted with a crucial question: Should chemotherapy be added after surgical removal of the tumor? Despite solid scientific evidence and endorsement by oncology societies for multi-gene tests supporting therapy decision making in breast cancer, only a small percentage of women are able to safely skip chemotherapy thorough personalized medicine.

The medical decision to add chemotherapy in breast cancer is a balance of the benefits of avoiding future recurrence of the tumor against the treatment toxicity and impact on the quality of life of the patient. Oncologists mostly rely on estrogen, progesterone-receptor and HER2 expression in the cancer tissue to guide endocrine therapy and targeted therapies, while chemotherapy is prescribed to most women.

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Now oncologists have irrefutable evidence that genomic testing of breast cancer tissue removed after surgery can help guide decisions to spare chemotherapy in up to 50 percent of patients. There are several multi-gene tests available that differ in their degree of scientific and clinical validation data. Three studies published in the New England Journal of Medicine in 2004, 2015 and 2016, and several others in top-tier oncology journals, have provided over the last decade the scientific and clinical credibility needed to incorporate these tests into clinical practice.

In 2004, the Oncotype DX recurrence score was shown to predict patients most likely to respond to chemotherapy in addition to endocrine therapy in women with early-stage cancer. In 2015, a prospective study showed that chemotherapy could be safely skipped in women with a low score. These women did not appear to benefit from the addition of chemotherapy regardless of other factors, such as positive lymph nodes.

A study published in August 2016 showed that the multi-gene test MammaPrint, FDA-approved, can also predict the clinical outcome in breast cancer. The study concluded that approximately 46 percent of women might not require chemotherapy despite having high risk based on clinical, non-genomic indicators. EndoPredict and Prosigna are other multi-gene tests for breast cancer also available to oncologists.

The most reputable professional oncology societies around the world have endorsed the clinical utility of multi-gene tests in breast cancer. The American Society of Clinical Oncology published in February 2016 that there is sufficient evidence supporting the clinical utility of the multi-gene tests in specific subgroups of breast cancer. The 2016 guidelines for breast cancer treatment of the National Comprehensive Cancer Network states that Oncotype DX helps determine in individual patients the likelihood of recurrence and benefit from chemotherapy.

While about 80 percent of breast cancer are diagnosed in the invasive state, about 20 percent are non-invasive, just confined to the ducts of the mammary glands, so-called ductal carcinoma in situ. The  test determines the likelihood of the tumor returning as invasive breast cancer in the same location.

Unfortunately, the slow adoption by the medical community of genomic tests in breast cancer is not an exception, it is the rule. The adoption of other gene tests such as BrCa and other hereditary genes is similarly disappointing.

The medical community is trailing behind spectacular advances in genomics, starting with the discovery of the function of genes in 1941, DNA decoding in 1953, the sequencing of the complete human genome in 2001, epigenomics emerging from junk DNA in 2012 and the creation of massive databases with cancer genomes from thousands of patients in recent years.

These breakthrough scientific advances are helping us understand how oncogenes and tumor suppressor genes are switched on and off, what pathways lead to cancer, how to manipulate these genes and be able to predict recurrence and metastatic potential of a tumor. Now is the time for patients and physicians to acknowledge the science and make decisions more personal.

Oscar Segurado, MD, PhD, Director of Medic Affairs Consulting LLC, has extensive global experience covering oncology, immunology and molecular biology in academia and industry settings.


The views expressed by contributors are their own and not the views of The Hill.