October 18, 2021
This guest article comes from Denise Croix, Ph.D., scientific liaison, medical and scientific affairs, at Roche Diagnostics Corporation.
When my mother was diagnosed with breast cancer 32 years ago, the doctors prescribed Tamoxifen, an important advance at the time since it targets cancer cells and does not have the side effects associated with chemotherapy. However, the doctors were uncertain about the duration of her therapy—for the rest of her life? Ten years? Five years? Since there were few treatment options, she also underwent a mastectomy. Fast-forward to 2016, when my first cousin on my mother’s side was diagnosed. This time, a combination of lumpectomy, radiation therapy and an oral drug was prescribed, based on her diagnosis and assessment of the likelihood of recurrence. While my mother and my cousin are both cancer survivors, my cousin’s smoother path to remission was paved in part by the armamentarium of diagnostic tools available. Indeed, while the incidence of breast cancer has held steady over the past 20 years—with an estimated 281,550 new cases in the U.S. in 2021—the mortality rate has steadily declined. According to the American Cancer Society, breast cancer has a five-year relative survival rate of 90.3%.
Enter precision medicine
The improvement in survival can be attributed to new developments in treatment and, just as important, the deeper understanding of this complex disease and our ability to diagnose breast cancer at the molecular level. Pinpointing the type of breast cancer and its origin enables the physician to deliver personalized treatment for each patient—a concept known as precision medicine. By identifying genes, proteins and other substances in the body, precision medicine helps your doctor tailor treatments—selecting treatments most likely to benefit the patient, while sparing the patient from those that are not likely to help. Scientists and doctors refer to these genes, proteins and other substances that can guide diagnosis and treatment as biomarkers. The identification of the biomarkers, unique to each patient, is the basis of an accurate diagnosis—telling the doctor exactly which specific cancer the patient has and therefore which treatments are the most effective.
Biomarkers of breast cancer
For an understanding of the role of biomarkers in cancer diagnosis, it is important to note that cancer cells are associated with abnormalities in their genes, such as having more than the normal number of copies of a gene (amplification), above-normal production of the protein encoded by the gene (overexpression), or abnormalities in the DNA sequence of the gene (mutation). Biomarker testing looks for the products (proteins) produced by the genes, or directly at the genetic makeup of the disease tissue. Today, three major biomarkers account for about 80% of breast cancer—estrogen receptor (ER), progesterone receptor (PgR) and human epidermal growth factor receptor-2 (HER2). Together, ER and PgR are referred to as hormone receptors (HR).
HR-positive/HER2-negative accounts for 68% of breast cancer and has the most favorable survival rate, with many therapy options.
Ranking second in survival rate is HR-positive/HER2-positive, which accounts for 10% of breast cancer. A number of therapies are available that target the HER2 receptor on the tumor cells.
Ranking third in survival rate is HR-negative/HER2-positive, accounting for 4% of breast cancer.
Triple-negative breast cancer (HR-negative/HER2-negative), sometimes called TNBC, accounts for 10% of breast cancer and has the least favorable survival rate. A new class of therapeutics known as immune checkpoint inhibitors is now available for TNBC patients.
Breast cancer biomarkers are most commonly identified using immunohistochemistry (IHC), which detects and identifies the proteins in breast tissue obtained through biopsy. Next generation sequencing (NGS), another diagnostic tool, is used to identify other potential mutations as well as determine risk of recurrence. Another commonly used diagnostic tool is gene expression profiling, which can help assess the likelihood of metastasis. A higher risk of metastasis may suggest a more aggressive treatment plan.
Early diagnosis is key
According to the National Cancer Institute, survival rate today is 99% at five years, if the tumor is diagnosed while still localized to the breast. Survival rate falls to 85.8% once the tumor has spread to local lymph nodes and to 29% for cancer that has metastasized to other sites. These statistics reinforce the importance of routine screening. Currently, the American Cancer Society recommends annual mammography for women between 45 and 54, then every two years after the age of 55. A new development in mammography called digital breast tomosynthesis, also known as 3D mammography, is sometimes recommended for women with dense breasts. For higher-risk patients, mammography may be supplemented with MRI.
A bright future
Based on improved survival rates over the years, and continuing research, there is every reason to be optimistic. But it all comes back to arming the doctor with early and accurate diagnosis. By leveraging advancing technology to characterize the cancer at the molecular level and thus enable targeted treatment, we can empower the patient to be an active participant in driving a positive outcome.
Learn more about Roche Diagnostics’ commitment to fighting breast cancer in the United States.
This article originally appeared in the Indiana Business Journal.