A new laboratory testing kit is now available that may help more accurately predict the risk of breast cancer recurrence after anti-hormone treatment. The developers of the test say it is a step toward personalized medicine and may help lower morbidity in patients with breast cancer.
“It is a milestone,” said oncologist Matthew Ellis, BSc, MB, BChir, PhD, FRCP, co-inventor of the test and a professor of medicine at Washington University School of Medicine, in St. Louis, MO. “This is the first test of its type.”
The test is called Prosigna™ (NanoString Technologies, Seattle, WA), and includes the ancillary equipment for its use so that patients’ tumor samples do not have to be sent to a specific laboratory for analysis. Currently, it is being distributed to pathology labs around the world. Even though it just received approval from the US Food and Drug Administration (FDA), it is already being used in the European Union.
This test categorizes breast tumors into one of four main types—luminal A, luminal B, human epidermal growth factor receptor-2 (HER2)–enriched, and basal-like—by looking at the expression of 50 genes. Each subtype has a distinct genetic signature and requires a different treatment approach, said Dr. Ellis during an interview with ChemotherapyAdvisor.com. The data on the individual subtype are combined with a standard pathology variable to deliver a “risk of recurrence” score that predicts the likelihood of a patient’s disease returning within the next 10 years.
Dr. Ellis explained that oncologists now may be better able to more accurately identify low-risk patients with breast cancer for whom standard hormone therapy is sufficient. Recently, this new test was compared with the Oncotype DX recurrence score, which is commonly used to estimate the risk of recurrence in women with estrogen receptor–positive (ER-positive) early breast cancer.1
The study included 1,017 women with ER-positive primary breast cancer treated with anastrozole or tamoxifen. The researchers found that the Prosigna test provided more prognostic information in endocrine-treated patients with ER-positive, node-negative disease than the Oncotype DX recurrence score, with better differentiation of intermediate-risk and higher-risk groups. “With this test, we can more accurately tailor the decisions about who gets chemotherapy and who can be treated with monotherapy with an endocrine agent alone,” Dr. Ellis said.
According to Dr. Ellis, the Prosigna test removes some of the subjectivity that goes into breast cancer diagnosis. Currently, the diagnosis is primarily accomplished by looking at the cells under a microscope and deciding on a likely outcome based on visual cues from the tumor. However, Dr. Ellis noted, there can be considerable variability in the tumor samples when observing them under a microscope, and this new test is an important new step toward a standardized diagnosis based on the genetics of the tumor.
“You can’t tell what the biology of a tumor is by just looking down the microscope and giving it a grade. It is based on appearance, which is a rather subjective look. The molecular test gives a more definitive picture as to the tumor’s biology,” said Dr. Ellis.
He hopes this test will help lower morbidity, and possibly mortality, in this patient population once it is widely adopted. The major determinant for or against chemotherapy is currently based on the risk of distant recurrence among women with ER-positive early breast cancer. Dr. Ellis said the Prosigna test may better define a women’s individual risk and lead to a change in treatment management for up to one-third of patients.
The Prosigna™ test was developed through a collaborative effort by researchers at the University of North Carolina, the University of Utah, and the BC Cancer Agency in Canada The universities jointly hold a pending patent on the technology behind the Prosigna test and have licensed the technology to Bioclassifer LLC.
- Dowsett M, Sestak I, Lopez-Knowles E, et al. Comparison of PAM50 risk of recurrence score with oncotype DX and IHC4 for predicting risk of distant recurrence after endocrine therapy. J Clin Oncol. 2013; 31(22):2783-2790.