Landmark international trial provides strongest evidence yet that a test co-invented and co-developed by UBC’s Dr. Torsten Nielsen can spare many high-risk breast cancer patients from chemotherapy and its potentially serious side effects
Millions of people with breast cancer could safely avoid chemotherapy thanks to a genomic test co-invented and co-developed by UBC Faculty of Medicine professor Dr. Torsten Nielsen, according to results from a major international clinical trial involving more than 4,400 patients with high-risk breast cancer.
Developed through two decades of research led by Dr. Nielsen and collaborators, the Prosigna test analyzes the activity of 50 genes within a breast tumour to identify its molecular subtype and estimate the risk of the cancer returning. The test results can then be used to help guide treatment decisions for people with hormone-sensitive breast cancer, providing critical insights on how likely a patient is to benefit from chemotherapy.
The new findings come from the international OPTIMA trial, which examined whether Prosigna could help identify patients who could safely forgo chemotherapy without compromising their long-term outcomes.
The findings, recently presented at the American Society of Clinical Oncology (ASCO) annual meeting, showed that breast cancer patients aged 40 and older with a low score on the Prosigna test had nearly identical outcomes whether they received chemotherapy or hormone therapy alone, despite having breast cancer that had already spread to nearby lymph nodes.
The results show many patients worldwide could be spared the physical and emotional burden of chemotherapy without increasing their risk of cancer recurrence.
“This global validation is an exciting and practice-changing milestone for patients here in Canada and around the world,” said Dr. Nielsen, a professor of pathology & laboratory medicine and director of the MD/PhD program at the UBC Faculty of Medicine. “For many people diagnosed with breast cancer, one of the most difficult questions is whether chemotherapy is truly necessary. These results provide strong evidence that we can take a precision medicine approach and identify many patients who can safely avoid chemotherapy while maintaining excellent outcomes.”
From UBC research to clinical impact
The scientific roots of Prosigna trace back to the early 2000s, when Dr. Nielsen and colleagues set out to investigate why patients with seemingly similar breast cancers often experienced dramatically different outcomes.
Working in collaboration with Dr. Charles Perou (University of North Carolina-Chapel Hill), Dr. Matthew Ellis (formerly of Washington University) and Dr. Philip Bernard (University of Utah), Dr. Nielsen helped develop a ‘genomic signature’ or test, known as PAM50, which reduced thousands of potential genetic markers to a set of only 50 genes capable of identifying distinct biological subtypes of breast cancer and estimating risk of cancer recurrence.
This breakthrough—which provided a standardized way to classify breast tumours based on their biology, rather than relying solely on traditional measures, such as tumour size or stage—was the scientific foundation of Prosigna.
Dr. Nielsen subsequently played a leading role in several pivotal research studies conducted in Vancouver that helped transform the laboratory innovation into a clinically approved diagnostic test. The resulting evidence ultimately paved the way for regulatory approvals of Prosigna in Canada, the United States and Europe.
Today, Prosigna has been adopted in multiple countries, including Spain, Norway, Denmark, Germany and France, and has helped to guide treatment decisions for thousands of patients.
“It is incredibly rewarding to see research that began here at UBC helping patients globally,” said Dr. Nielsen. “When we started this work more than two decades ago, we were trying to understand why breast cancers that looked similar behaved so differently. Today, we’re seeing that knowledge and our research efforts translated into better care for patients worldwide. That’s the ultimate goal of cancer research.”
International trial confirms clinical value
The OPTIMA trial provides some of the strongest evidence to date that the genomic test can safely reduce unnecessary chemotherapy use in a broad group of patients.
Trial participants (over 90 percent of whom had node-positive breast cancers) had their breast mass surgically removed and then were randomly assigned to receive either standard treatment—which included chemotherapy followed by hormone therapy—or treatment guided by Prosigna test results. Patients with high Prosigna scores received chemotherapy and hormone therapy, while those with low scores received hormone therapy alone.
“It is incredibly rewarding to see research that began here at UBC helping patients globally.”
Dr. Torsten Nielsen
Among the 4,429 patients enrolled in the study, more than two-thirds (68 per cent) had low Prosigna scores. Five years after treatment, 95% of patients with low Prosigna scores who received chemotherapy and hormone therapy were alive and free from breast cancer recurrence, compared with 94% of those treated with hormone therapy alone.
The findings—which indicate chemotherapy, with its sometimes toxic side effects, provides no net benefit for patients with low Prosigna scores—are expected to change how breast cancer is treated moving forward.
“Chemotherapy remains an important and lifesaving treatment for many people with breast cancer,” said Dr. Nielsen. “The challenge has always been determining who truly needs it. Genomic tools like Prosigna allow us to move beyond traditional clinical factors to better understand the biology of each individual tumour, helping ensure patients receive the treatment most likely to benefit them.”
The OPTIMA trial was led by researchers at University College London and the University of Glasgow and included participants from the United Kingdom, Norway, Sweden, Australia, New Zealand and Thailand. Read University College London news release to learn more.
