Research team finds aggressive breast cancers are less frequent than previously thought, and less aggressive breast cancers need more of our attention.

Different subtypes of breast cancer respond to treatment differently and require different treatment approaches. Understanding the distribution of these subtypes and their respective clinical outcomes allows researchers to better understand the disease and identify key research priorities that may have been previously overlooked.

Dr. John Bartlett, Program Director of Diagnostic Development at OICR, and a team of collaborators in the U.K. have investigated the proportion of women with common breast tumour types across 199,300 breast cancer patient records. Their study, which was recently published in The Journal of Pathology: Clinical Research, provides new and robust benchmarking figures for the distribution of common subtypes of the disease, including estrogen-receptor (ER) positive and negative breast tumours.

“With this robust benchmarking data we can better understand the prevalence of different breast cancers and strengthen the evidence-base for clinical breast cancer testing,” says Bartlett.

In this study, the research group found that the most aggressive types of the disease – ER-negative breast cancers – are only half as common as currently quoted in literature. In contrast, a form of the disease that is often regarded as more manageable and treatable– ER-positive breast cancer – is more common than previously thought, with 83 per cent of breast cancer patients having ER-positive disease rather than 70 per cent.

“For breast cancer patients with ER-positive tumours, we know that their risk of relapse remains consistent for almost twenty years after treatment,” says Bartlett. “This means that despite being more treatable at diagnosis, the prevalence and pernicious nature of ER-positive breast cancer makes it the second leading cause of cancer death in women.”

With a longstanding track record of research in breast cancer research, especially in ER-positive cancers, Bartlett and his research group will continue to develop novel diagnostic tools to identify molecular subtypes of breast cancer and to predict the effectiveness of treatment.

“This study reinforces that ER-positive breast cancer is the silent epidemic of breast cancer and deserves more of our attention,” says Bartlett. “We’re working to find new and better solutions for patients with this disease.”