Fri. Jan 21st, 2022

TORONTO, December 7, 2021 / CNW / – A widespread and inexpensive type 2 diabetes drug that once hoped to provide a huge promise for the treatment of breast cancer does not prevent or stop the spread of the most common forms of the disease according to new results.

Sinai Health Logo (CNW Group / Sinai Health Foundation)

Sinai Health Logo (CNW Group / Sinai Health Foundation)

The landmark lawsuit, led by Dr. Pamela Goodwin at Sinai Health and run by the Canadian Cancer Trials Group (CCTG) under the umbrella of the Breast International Group (BIG) network, is the largest of its kind to date and tracks more than 3,600 breast cancer patients from around the world Canada, USA, Switzerland and the United Kingdom

The randomized, double-blind trial included patients treated with two pills a day with either placebo or the diabetes drug metformin. Overall, researchers found that the addition of metformin to standard breast cancer treatments did not improve outcomes in the two most common types of breast cancer, hormone receptor-positive or negative.

“The results tell us that metformin is not effective against the most common types of breast cancer, and any off-label use of this drug to treat these common types of breast cancer should be stopped,” said Dr. Goodwin.

Dr. Goodwin is a medical oncologist at Sinai Health and a clinician at the Lunenfeld-Tanenbaum Research Institute in Toronto. Dr. Goodwin presented the results Tuesday at the San Antonio Breast Cancer Symposium in 2021. The results have yet to be peer-reviewed.

While metformin has not been shown to be effective in treating the most common forms of breast cancer, Dr. Goodwin that the trial found a potentially important result for people with a less common but aggressive form of the disease, called HER2-positive breast cancer.

For this subtype of breast cancer, the researchers found that there was evidence that metformin use for five years could lead to a reduction in deaths. HER2-positive cancer accounts for about 20 percent of all breast cancer cases.

“Metformin is not beneficial for use in most common forms of breast cancer, but in the case of HER2-positive breast cancer, our results suggest that it may be beneficial,” said Dr. Goodwin. “These findings need to be replicated in future research before metformin is used as a breast cancer treatment, but it could provide an additional treatment option for HER2-positive breast cancer.”

Metformin belongs to a class of medicines called biguanides, which are used to treat high blood sugar or diabetes. Previous observational and preclinical studies have suggested that metformin may also reduce the risk of developing and increase the survival of some cancers, including breast cancer. It was theorized that the drug can slow the growth of breast cancer by improving the patient’s metabolism, especially insulin levels, leading to reduced growth of cancer cells, or that it can directly affect cancer cells.

The results have been sent for publication. A potential next step would be to prospectively test the effect of metformin in patients with HER2-positive breast cancer in a randomized clinical trial.

The multinational experiment was run by the CCTG with the support of several licensing agencies along with a large team of scientists, including Dr. Goodwin, Dr. Vuk Stambolic at the Princess Margaret Cancer Center in Toronto, and Drs. Wendy Parulekar and Bingshu Chen at CCTG.

“The CCTG MA.32 study illustrates the importance of international academic group collaboration to test new treatment approaches with a goal of promoting clinical care,” said CCTG Senior Investigator Dr. Wendy Parulekar. “The results of all Phase III trials inform about current treatment standards and generate hypotheses to be tested in future studies. CCTG is grateful to all patients and families, healthcare teams, grant agencies and collaborators who enabled the trial to be successful.”

This research was funded by the Canadian Cancer Society, the National Cancer Institute (US), the Canadian Breast Cancer Foundation, the Breast Cancer Research Foundation, Cancer Research UK, Hold’Em for Life Charity Challenge and Apotex (Canada).

About Sinai Health
Sinai Health consists of Mount Sinai Hospital, Hennick Bridgepoint Hospital, Lunenfeld-Tanenbaum Research Institute and its system partner Circle of Care. It provides excellent care in the hospital, in the community and at home, focusing on the comprehensive needs of people. Sinai Health detects and translates scientific breakthroughs, pushes boundaries of healthcare solutions, and trains future clinical and scientific leaders. Clinical areas of specialization include rehabilitation and complex persistent care, surgery and oncology, acute and critical care, and women’s and infants’ health. Its Lunenfeld-Tanenbaum Research Institute is among the 10 best biomedical research institutes in the world. Sinai Health is a full affiliate of University of Toronto.

About the Canadian Cancer Trials Group
The Canadian Cancer Trials Group (CCTG) is a clinical cancer research cooperative running Phase I-III trials to test anti-cancer and supportive care treatments in over 85 hospitals and cancer centers across Canada. From the Operations Center at Queen’s University, CCTG has supported more than 600 trials enrolling 100,000 patients from 40 countries on 6 continents through a global network of 20,000 investigators and clinical trial staff. CCTG is a national program of the Canadian Cancer Society and their goal is to improve the survival and quality of life of all people with cancer.

About Breast International Group (LARGE)
The Breast International Group (BIG) is an international non-profit organization for academic breast cancer research groups from around the world, based in Brussels, Belgium.

Global collaboration is essential to make significant progress in breast cancer research, reduce unnecessary duplication of work, share data, contribute to faster development of better treatments and increase the likelihood of healing patients. Therefore, BIG facilitates breast cancer research at an international level by stimulating collaboration between its members and other academic networks and collaborating with, but working independently of, the pharmaceutical industry.

In 1999, BIG was founded by Dr Martine Piccart and Dr Aron Goldhirsch with the aim of addressing fragmentation in European breast cancer research. Research groups from other parts of the world quickly expressed interest in joining BIG, and two decades later, BIG represents a network of over 50 like-minded research groups from around the world. These units are linked to thousands of world-class specialist hospitals, research centers and breast cancer experts across approximately 70 countries on 6 continents. More than 30 clinical trials are being run or are under development under the BIG umbrella at any given time. BIG also works closely with the US National Cancer Institute (NCI) and the National Clinical Trials Network (NCTN) to work together as a strong integrative force in the breast cancer research arena.

BIG’s research is supported in part by its philanthropy unit, known as BIG against breast cancer. This term is used to interact with the general public and donors and to raise funds for BIG’s purely academic breast cancer trials and research programs. For more information, visit

SOURCE Sinai Health Foundation



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