Skip to main content
An official website of the United States government

TMIST: Study Comparing Digital Mammograms (2-D) with Tomosynthesis Mammograms (3-D)

TMIST will help researchers learn about the best ways to find breast cancer in women who have no symptoms. 

Credit: iStock

TMIST (Tomosynthesis Mammographic Imaging Screening Trial) is a research study that will help researchers learn about the best way to find breast cancer in women who have no symptoms. It is a randomized breast cancer screening study that compares two types of Food and Drug Administration (FDA)-approved digital mammograms for their ability to reduce advanced breast cancer: standard digital mammograms (2-D) and a newer technology called tomosynthesis mammograms (3-D). 2-D mammograms take pictures from two sides of the breast to create a flat image. 3-D mammogram images are taken from different angles around the breast and then built into a 3-D-like image.

The goal of breast cancer screening is to find life-threatening breast cancer early, when it may be easier to treat, and reduce the chance that someone will die from it. Researchers are doing this trial because they do not know if 3-D are better than 2-D mammograms for breast cancer screening.

Who can enroll in TMIST?

People aged 45 to 74 who are planning to get a routine screening mammogram are eligible for this trial. You can also contact a site that is taking part to ask about joining the study. Open sites are listed in the Locations & Contacts section of the TMIST summary page.

How do I enroll in TMIST?

When you schedule a routine mammogram, you may be asked if you would like to take part in TMIST. The trial is taking place in mammogram clinics around the United States, with a few sites in Argentina, Canada, Italy, Korea, and Peru. Over 100 clinics are taking part in the trial. 

Researchers plan to enroll nearly 129,000 people.

What happens once I enroll in TMIST?

TMIST will last for 5 years. Once enrolled, you will be randomly assigned by a computer to have either a 3-D or 2-D screening mammogram. You will have that kind of mammogram every year or every other year for 5 years. How often you have a mammogram during these 5 years will be based on your

How often you have a mammogram during the 5 years of the study may change if your risk changes.  Risk changes might include new genetic testing findings, changes in family history, or changes in hormone replacement therapy use.

During the study, the results of every mammogram from every participant will be collected. Information will also be recorded about any medical follow-up tests, such as more imaging or a biopsy, breast cancer diagnoses, treatment, and how people responded to treatment.

How will people be followed after taking part in TMIST?

After you complete 5 years on the study receiving the type of mammogram that was assigned, the research team will follow you for another 3 years. During the 3-year follow-up period you can get either type of mammogram.

What are the goals of TMIST?

Even though some 3-D mammogram machines are FDA approved, no one knows if 3-D mammograms are better than 2-D at finding life-threatening breast cancers early enough that they can be treated successfully. 

Therefore, the main goal of TMIST is to compare 2-D mammograms with 3-D mammograms to see which one is better at reducing advanced breast cancer. If one type of mammogram is better at finding life-threatening breast cancers early, then fewer people screened with that type of mammogram should go on to develop advanced breast cancer.      

The researchers are also looking at whether 3-D mammograms might help certain groups of women. Questions they are trying to answer include

  • Among the women who receive 3-D mammograms, will fewer advanced cancers be diagnosed in certain groups, such as
    • women with dense breasts
    • different  racial and ethnic groups
    • premenopausal women
    • women who are taking hormone replacement therapy
  • Will there be fewer false-positive test results in the entire study group or among certain groups?
  • Is there a link between certain findings on mammograms and development of the most aggressive breast cancers?
  • Are some types of cancers more common between recommended screening intervals?

Another important aspect of the trial is to build a tissue bank for future research. Everyone who joins the trial will be asked to submit tissue samples, such as blood and swabs of cells from inside their mouths. Researchers hope that the information from these tissue samples will help personalize the way we screen for breast cancer in the future by taking a person’s genetics and other personal risk factors into account.

What happens if I am diagnosed with breast cancer while taking part in TMIST? 

If you have a mammogram while taking part in TMIST that leads to a biopsy, the tissue collected from that biopsy will be analyzed as part of the study. Studying this tissue, whether it is benign, precancer, or cancer, will help researchers learn more about the biology of breast cancers that are found through mammograms.

If the biopsy shows that you have breast cancer, you will be treated for your cancer just as you would if you were not part of TMIST. Although treatment for breast cancer is not provided as part of the study, the study team will collect information on all the tests, procedures, and treatments used to diagnose and treat the cancer. Procedures and treatments that you might have include imaging, biopsies, surgery, chemotherapy, and radiation therapy. See our page about Breast Cancer Treatment for more information.

Are there costs to taking part in TMIST?

Your health insurance will be billed for the cost of the mammogram during your time on the study. Some health plans do not cover the complete cost of a 3-D mammogram. So, if you are randomly assigned to receive 3-D mammograms and your plan will not cover the complete cost, you may need to pay for the portion that the health plan will not cover. This is the same as if you were not part of the study. You will not be paid to take part in this study.

TMIST Collaborators

TMIST is supported by NCI and is coordinated by the ECOG-ACRIN Cancer Research Group.