Delving into the emerging world of personalized medicine, researchers at the University of South Florida have presented the results of a study they say enforces the value of genetic subtyping in the treatment of breast cancer.
The USF investigators, led by Charles Cox, the McCann Foundation Endowed Professor of Breast Surgery at the USF Health Morsani College of Medicine, looked into why different types of gene testing of breast cancer patients can sometimes reach conflicting conclusions on a breast cancer patients prognosis.
The study compared two methods of assessing the likelihood of breast cancer recurrence, genomic testing and molecular subtyping. If this sort of testing reveals the type of malignancy a breast cancer patients has a low risk of recurrence, the patient might be able to forgo post-surgical chemotherapy and undergo hormone therapy instead. The patient would be able to avoid the cost of chemotherapy and its often-unpleasant side effects.
“The most important takeaway for our colleagues in breast cancer diagnosis and treatment is the potential value of molecular subtyping to personalize and improve each woman’s treatment,” said Cox.
The findings of the USF researchers were presented last week at the 2014 Miami Breast Cancer Conference, in Miami Beach.
One of the study’s most important findings involved three widely used forms of genomic testing, Oncotype DX, MammaPrint and Mammastrat. They were thought to deliver roughly the same assessment of the risk of breast cancer recurrence, but the USF test found that wasn’t the case.
For example, the USF researchers, working with tissue samples from 148 breast cancer patients found the greatest lack of agreement on recurrence risk among a group of 51 patients. The MammaPrint results suggested all 51 were at high recurrence risk, while Oncotype DX classified 35 as at low risk.
The genetic subtyping test used in the study was BluePrint, developed by Agendia NV, a Netherlands-based molecular diagnostic company. Subtyping, Cox said in a recorded interview, does a good job of determining which breast cancer patients are at low and high risk of recurrence.
Research has identified four breast cancer subtypes:
• HER-2-positve, which tends to be aggressive and doesn’t respond well to hormone therapies.
• Basal-like/triple negative, which is aggressive and has a poor treatment prognosis.
• Luminal A, which has a positive prognosis and low recurrence risk.
• Luminal B, which is prone to early relapse after hormone therapy.
BluePrint testing of the samples from the 51 patients MammaPrint identified as high risk were the luminal B subtype.
The lack of agreement on risk by differing genomic tests, known as discordance, doesn’t mean any of the test results are wrong, Cox stressed.
“These tests use different genes and were validated on different types of populations,” he said. “But if physicians use molecular subtyping as we did in this study, they will have valuable, additional information to guide the appropriate treatment for each patient.”
Using molecular subtyping in combination with traditional biomarkers such as tumor grade and hormone receptor status for determining the biological nature of cancer is a recommended guideline for breast cancer treatment in both the United States and Europe, Cox said.
The additional information provided by genomic tests and molecular subtyping may help reduce overall treatment costs for breast cancer by targeting chemotherapy only for those women who will benefit from it, Cox said “Personalized treatment guided by these tests may also extend the time that patients are free of their cancer,” he said.
Collaborators at Florida Hospital Tampa, Morton Plant Hospital, in Clearwater, and Agendia took part in the USF study. Cox and another study participant, Morton Plant Comprehensive Breast Care Center of Tampa Bay surgeon Peter Blumencranz, are members of the Agendia advisory board and its speakers bureau.