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Canadian women are now able to participate in a large North American breast cancer screening trial

MAC.22 (TMIST) screening for breast cancer with tomosynthesis mammography
Wednesday, May 23, 2018

The Sunnybrook Health Sciences Centre and the Ottawa Hospital are currently enrolling women in the Tomosynthesis Mammographic Imaging Screening Trial (TMIST), the first randomized trial to compare conventional mammography (2-D) to the newer digital tomosynthesis method (3-D).

The large scale North American study was developed by the US based ECOG-ACRIN Cancer Research Group (ECOG-ACRIN) and the National Cancer Institute (NCI), with the Canadian Cancer Trials Group (CCTG) coordinating the trial in Canada (more national sites will be opening the trial over the next several months).

“There is no science to show that seeing more makes 3-D any better than 2-D at finding more of the aggressive types of breast cancer early,” said ECOG-ACRIN study chair Etta D. Pisano, MD, professor in residence at Beth Israel Deaconess Medical Center and Harvard Medical School, and chief science officer at the Center for Research and Innovation at the American College of Radiology. “This trial is not only about which technology works best, it is about how we can help individual women get what they need to avoid death from breast cancer.”

“We should always base decisions about adopting new medical technologies on scientific evidence,” said Martin J. Yaffe, PhD, the Tory Family Chair of Cancer Research at Sunnybrook Health Sciences Centre and the lead researcher for the Canadian arm of the trial. “TMIST will provide solid evidence as to the impact that we can expect in reducing the burden of breast cancer on women and their loved ones.”

More than 3000 Canadian women participated in a lead-in study led by Dr. Yaffe that helped inform TMIST and some of them have already agreed to join the current larger trial, which will enroll nearly 165,000 women in the US and Canada by the end of 2020.

Franca Piacente from Toronto is enrolled in the trial at Sunnybrook Health Sciences Centre and she says: "It was important to me to participate to help our healthcare researchers identify the best and most effective way of screening women for breast cancer”.

The TMIST trial is for healthy women ages 45 to 74 who are already planning to get a routine mammogram. The participants will provide critical information that will inform the study, which seeks to change breast cancer screening to a more personalized approach.

About the MAC.22 (TMIST) trial

The Tomosynthesis Mammographic Imaging Screening Trial (TMIST), is the first randomized trial to compare two types of digital mammography for breast cancer screening: tomosynthesis (known as three-dimensional, or 3-D) and conventional (two-dimensional, or 2-D). Although 3-D mammography, is a newer technology it will likely detect more findings that require follow-up, it is also likely to lead to more procedures and treatments. It is not known if this newer mammography technology is reducing a woman’s risk of developing a life-threatening (advanced) cancer compared with 2-D mammography.

At participating centers, women (45 to 75) will be told about the trial when they schedule their routine mammogram and once enrolled are then randomly assigned to either 2-D or 3-D mammography screening for the next five years.

To find out more about the trial and where it is available for enrollment in Canada please visit:


(AP Video/Kathy Young)