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Lois Shepherd, MDCM, FRCPC
Professor, Department of Pathology and Molecular Medicine
Queen's University, Kingston
National Cancer Institute Canada Clinical Trials Group
Goal: To identify alternative chemo-preventive strategies for breast cancer patients with a high risk of recurrence.
Impact: Insulin and insulin growth factor (IGF) pathways appear to play a role in the development and recurrence of breast cancer. Dr. Shepherd has been studying the drug metformin, which is widely prescribed for diabetes, to determine if it can prevent recurrence. If so, metformin could provide a non-hormone-based approach to breast cancer prevention.
What’s next: Dr. Shepherd will continue to conduct a randomized phase III trial of metformin compared with placebo to evaluate its effect on recurrence and survival in early stage breast cancer.
Metformin is a commonly used drug that treats the metabolic disorders associated with Type 2 diabetes and has been shown to reduce risk of recurrence in breast cancer patients with diabetes. However, it may also benefit non-diabetic women with breast cancer because it blocks the major pathways that promote tumor growth. Dr. Shepherd is conducting an international study in women with early stage breast cancer to determine the effectiveness of metformin in preventing recurrence.
Full Research Summary
Research area: Determining whether metformin, which is widely prescribed for diabetes, could prevent breast cancer recurrences.
Impact: Over the last decade, there has been growing evidence that insulin and insulin growth factor (IGF) pathways play a role in the development and recurrence of breast cancer. Because metformin blocks the major pathways that promote tumor growth, it has gained interest as a potential preventive agent for non-diabetic women with a high risk of breast cancer recurrence. Dr. Shepherd is conducting a randomized phase III trial of the effect of metformin on recurrence and survival in early-stage breast cancer. If proven effective, metformin could provide a non-hormone-based approach to prevention.
What she’s learned so far: Previously reported results from the study—which is being conducted across North America, the United Kingdom, and Switzerland—showed that metformin had the expected effect of reducing body mass index, weight, glucose, and insulin levels. An interim analysis of the data suggests that patients with hormone receptor negative breast cancers are unlikely to benefit from metformin. The remainder of women in the study with estrogen receptor- and progesterone receptor-positive breast cancer will continue treatment.
What’s next: Dr. Shepherd continues following the study participants for events of breast cancer recurrence, with final results of the study expected in 2023. They are conducting analyses on the metabolic effects of metformin as well as its effects on DNA methylation – a non-genetic form of DNA regulation – and other markers related to cancer promotion.
Dr. Lois Shepherd is a Professor in the Department of Pathology and Molecular Medicine at Queen's University. She completed her medical school training at McGill and spent three years in England where her interest in hematology developed. She completed her training as a hematopathologist at the University of Ottawa and moved to Queen's University, Kingston, Ontario in 1987. Dr. Shepherd is currently the Director of the Transfusion Medicine Service and Immunology at Kingston General Hospital. Since 1989, Dr. Shepherd has worked with the Clinical Trials Group of the National Cancer Institute of Canada (NCIC CTG) as a Senior Investigator. Her focus has been in hematology and breast cancer as well as the development of the National Tumor/Tissue/Data Repository associated with the NCIC Clinical Trials Group, where she is the Operational Director of this resource.