The Tomosynthesis Mammographic Imaging Screening Trial, known as TMIST or study EA1151, is comparing two types of digital mammography approved by the Food and Drug Administration: tomosynthesis (known as three-dimensional, or 3-D) and conventional (two-dimensional, or 2-D). Although 3-D mammography, being the newer technology, is likely to detect more findings that require follow-up, it is also likely to lead to more procedures and treatments. It is not known if the newer technology is more effective than conventional 2-D mammography at reducing life-threatening (advanced) breast cancers. The TMIST trial aims to find out.

The ECOG-ACRIN Cancer Research Group opened the trial on July 6, 2017, and plans to enroll about 165,000 women by the end of 2020.

Who TMIST is For

In order to participate in the study, women must be

  • 45-74 years of age
  • Planning for routine screening mammograms

In addition, women must not

  • Be pregnant, intend to be pregnant, or lactating
  • Have symptoms of breast cancer
  • Have had a screening mammogram in the last 11 months
  • Have a history of breast cancer
  • Currently have breast implants or other breast enhancements

What Participants Can Expect

If a woman decides to participate, she will be involved in this research study for at least eight years starting with her next scheduled mammogram. During that time:

  • She will need to agree to be randomized (assigned by a computer) to get either 3-D or 2-D mammograms for the first five years of the trial
  • She will need to agree to let her doctor tell her how often to get screened during the first five years of the research study—either every year or every other year—based on her individual risks for developing breast cancer
  • Her breast cancer status will be followed for at least 8 years in total, including the screening years, by reviewing her medical records and possibly contacting her for a brief phone survey

Where the Trial Will be Available

The trial will take place at about 100 vetted mammography clinics, mostly in the United States and a few clinics in Canada. To ensure that TMIST enrolls a diverse group of women, the trial clinics will be located in large and small communities throughout the United States, and the women they serve will reflect the country’s racially and ethnically diverse population. The selected mammography clinics will join the trial on a rolling basis between the fall of 2017 and spring of 2018. Before opening the trial, each clinic must receive IRB approval, submit evidence of rigorous pre-testing of imaging equipment, and complete staff training requirements specifically for this trial. Follow this link to view trial locations

ECOG-ACRIN Website Resources for TMIST

Links to Helpful Resources on


Inquiries about TMIST may be directed to:
ECOG-ACRIN Cancer Research Group
Operations Office – Boston

TMIST Funding

TMIST is publicly funded by the National Cancer Institute, part of the National Institutes of Health, through the NCI Community Oncology Research Program.