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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
Ontario, Canada

Current Research

  • Seeking alternative chemopreventive strategies for breast cancer patients with a high risk of recurrence.
  • Analyses are ongoing to evaluate the effect of metformin on recurrence and survival in patients with early-stage breast cancer.
  • Metformin is a commonly prescribed diabetes drug and is both inexpensive and well tolerated. If confirmed by these studies, it could provide a non-hormone-based approach to prevention.

Metformin is a commonly used drug used to treat the metabolic disorders associated with Type 2 diabetes and has been shown to reduce risk of recurrence in breast cancer patients with diabetes. Because metformin blocks the major pathways that promote tumor growth, it has gained interest as a potential preventive agent for non-diabetic women with breast cancer at risk of recurrence. Dr. Shepherd is conducting an international study in women with early stage breast cancer to determine the effectiveness of metformin in preventing breast cancer recurrence. The study is fully enrolled, and patients will be followed through 2020.

Full Research Summary

Dr. Lois Shepherd of the NCIC Clinical Trials Group in Ontario, Canada, and BCRF colleague, Pamela Goodwin, have teamed up to conduct a randomized phase III trial of the effect of the anti-diabetes drug, metformin, on recurrence and survival in early-stage breast cancer. Metformin is a commonly used drug to treat adult-onset (Type 2) diabetes.

Over the last decade, a growing body of evidence has suggested that high levels of insulin resulting from diabetes may play a role in the development and recurrence of many cancers including breast cancer. Metformin inhibits the insulin pathway, and its potential use in preventing the recurrence of early-stage breast cancer is being explored in the MA.32 study.

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. A total of 3649 women participated in the trial of which 2259 were from the United States, 1203 were from Canada, and 187 from the UK and Switzerland.

An interim analysis of the data suggests that patients with hormone receptor (ER and/or PR) negative breast cancers are unlikely to benefit from metformin. The remainder of women on study with ER and/or PR-positive breast cancer will continue treatment for the full five years. Analysis of the data to determine the effectiveness of metformin in preventing breast cancer recurrence is ongoing, with final results anticipated in 2020.


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.

Grid Researcher Headshot - Shepherd L

BCRF Investigator Since


Donor Recognition

The ANN INC. Award (a division of ascena retail group inc.)

Area(s) of Focus