TMIST (Tomosynthesis Mammographic Imaging Screening Trial)

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The Trial

TMIST is a randomized breast screening trial that will help researchers learn about the best ways to find breast cancer in women who have no symptoms. It compares two Food and Drug Administration (FDA)-approved types of digital mammography: standard digital mammography (2-D) with a newer technology called tomosynthesis mammography (3-D). 2-D mammography takes pictures from two sides of the breast to create a flat image. 3-D mammography 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 breast cancer early when it may be easier to treat. Researchers are doing this trial because they do not know if 3-D is better than 2-D mammography for breast cancer screening.

Another important aspect of the trial is to build a tissue bank for future research. All women who join 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 decide the best ways to screen for breast cancer in the future by taking a person’s genetics and other personal risk factors into account.

Who Can Enroll in TMIST

Women ages 45 to 74 who are planning to get a routine screening mammogram are eligible for this trial. Women can also contact a participating site to ask about joining the study. Open sites are listed in the Locations & Contacts section of the trial record.

How to Enroll in TMIST

The trial is taking place in mammography clinics around the United States, with a few sites in Canada. Eventually, there will be about 100 clinics taking part in the trial. When women call one these participating clinics to schedule a routine mammogram, they may be asked to take part in TMIST.

Researchers plan to enroll nearly 165,000 women over 2 ½ years.

What Happens Once Women Enroll in TMIST

Once enrolled in the trial, women will be randomly assigned by a computer to receive either 3-D or 2-D screening mammograms for 5 years. How often they receive mammograms will be based on their:

For women ages 45 to 69, if any of the following factors apply, they will have one mammogram per year, for a total of five mammograms over 5 years:

  • Have regular periods, had their most recent period within the last 12 months, or are younger than 52 and have had a hysterectomy but still have ovaries
  • Have dense breasts        
  • Take hormone replacement therapy prescribed by a doctor         
  • Have a family history of breast cancer or genetic changes known to cause breast cancer

Women in this age group who have none of these factors will have a mammogram every 2 years, for a total of three mammograms over 5 years.

For women ages 70 to 74, if any of the following factors apply, they will have one mammogram per year, for a total of five mammograms over 5 years:

  • Have dense breasts        
  • Take hormone replacement therapy prescribed by a doctor         

Women in this age group who have neither factor will have a mammogram every 2 years, for a total of three mammograms over 5 years.

If a woman’s risk changes, it’s possible that the frequency and number of mammograms she receives will change during her time in the study. Risk changes might include new genetic testing findings or changes in family history or hormone replacement therapy use.

During the study, the results of every mammogram from every woman will be collected, whether the mammograms are normal or not. Information about any medical follow-up, such as more imaging or a biopsy, will also be recorded. All women will be followed until the end of the study for breast cancer status, treatment, and results from treatment.

Follow-Up after Completing TMIST

The study team will continue to follow women who have completed the trial for 3 years. During the follow-up period, women and their primary care doctors will decide on the type of mammogram they will have.

Goals of TMIST

Even though some 3-D mammography machines are FDA-approved, no one knows if 3-D mammography is better than 2-D at finding breast cancers before they become more difficult to treat. Therefore, the main goal of TMIST is to measure and compare the rates of newly diagnosed breast cancer that meet certain criteria. These criteria include:

  • Tumors that are at least as big as a nickel (20 millimeters or larger)
  • Tumors larger than 10 millimeters and HER2-positive
  • Tumors larger than 10 millimeters and triple-negative
  • Cancer has spread from the breast to at least one nearby lymph node
  • Cancer has spread from the breast to distant organs in the body

Researchers are also looking at whether 3-D mammography might help certain groups of women. Questions they are trying to answer include:

  • Among the women who receive 3-D mammography, will there be fewer harder-to-treat cancers in certain groups, such as those with dense breasts, African Americans, premenopausal women, and women on 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 from the mammograms and the most aggressive breast cancers?

What Happens If Women Are Diagnosed with Breast Cancer during the Study?

Most women will not be diagnosed with breast cancer during their time in the study. But, if they are, they will be treated just as they would if they were not part of the trial. Although treatment for breast cancer is not provided as part of the study, information on all procedures and treatments will be collected and kept for the purposes of TMIST. Examples of procedures and treatments include any imaging, biopsies, surgery, chemotherapy, and radiation therapy.

Tissue collected from breast biopsies will also be analyzed as part of the study. Studying this tissue will help researchers learn more about the biology of breast cancers that are found through mammography.

Who Pays for Trial Costs

Women’s health plans will be billed for the cost of the mammogram during their time in the study. Some health plans do not cover the complete cost of a 3-D mammogram. So, if a woman is randomly assigned to receive 3-D mammograms and her plan will not cover the complete cost, she may need to pay for the portion that the health plan will not cover, just as she would if she were not part of the study. Women will not be paid to take part in this study.

Trial Collaborators

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