New test will inform personalized breast cancer treatment

14 May 2009

A study published in May 2009 in the Journal of the National Cancer Institute shines more light on the pathology of breast cancer tumours.

The study, led by Dr. Torsten Nielsen – an MSFHR Senior Scholar, clinician-researcher with the Genetic Pathology Evaluation Centre at the Vancouver Coastal Health Research Institute and BC Cancer Agency, and associate professor in the UBC Department of Pathology and Laboratory Medicine – paves the way for more personalized treatment options for women diagnosed with hormone receptor-positive breast cancer. The Canadian Breast Cancer Research Alliance, MSFHR and the National Institutes of Health provided funding support for the study.

Currently, breast cancer treatment is prescribed based on the patient’s age, tumour size, lymph node involvement, and microscopically-determined grade and hormone receptor status. Approximately two-thirds of patients have tumours that are either estrogen or progesterone receptor positive, and they receive drugs such as tamoxifen or aromatase inhibitors which block the hormones that feed the tumour growth. This type of therapy has reduced breast cancer mortality by more than 30 percent, but not all women benefit and there is an important need to distinguish patients at high risk for recurrence who need more chemotherapy from patients at low risk, for whom adjuvant hormonal therapy alone may be sufficient.

Recent research into the molecular gene expression profiles of breast cancer has shown that hormone receptor positive breast cancers break down into two major types: Luminal A and Luminal B. The Luminal B tumors grow more quickly and are thought to require more aggressive treatment, because they are more likely to prove fatal. However the gene expression tests are very expensive and require specialized lab equipment that is not widely available. Dr. Nielsen and his team have devised a panel of simple, inexpensive antibody tests that can distinguish between these two types of hormone receptive tumours: Luminal A (low risk) and Luminal B (high risk).

“Previously, no simple test has existed that allowed us to differentiate the breast cancer molecular subtype on standard biopsy samples, and as a result, the differences between Luminal A and B breast cancers could not be used to guide treatment.” says Dr. Nielsen, a member of MSFHR's Research Advisory Council. “Our antibody test can be applied inexpensively to standard pathology specimens, and so far it seems to provide much of the clinically-important information gained from more complicated molecular tests.”

Dr. Nielsen and his team are already applying the test to clinical trials samples to find out which treatments work best. “We gave advance notice of our test to colleagues in Alberta and have found that a newer taxane chemotherapy works well for Luminal B patients, whereas Luminal A patients don’t get added benefit as their prognosis is very good regardless. We are applying our test to other clinical trials series with the hope that this will let us personalize decisions about which drugs are needed to give each patient her best chance of cure, while avoiding unnecessary risks for side effects.”