TMIST Ramps Up to Illuminate Breast Cancer Screening

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Wednesday, October 16, 2019, by DCP Staff

For the inaugural post of the Cancer Prevention Science blog, the focus is on the ongoing critical study of 2-D vs. 3-D mammography for breast cancer screening known as TMIST. Next time, Deborah Winn, PhD, acting director of the Division of Cancer Prevention, will answer questions about this research blog, and about the future of cancer prevention science.

TMIST (Tomosynthesis Mammographic Imaging Screening Trial), the large NCI screening study to learn about the best ways to find breast cancer in women who have no symptoms, is ramping up with 16,505 participants enrolled to date at 84 certified mammography clinics in the United States, Canada and Argentina.

Photo of Etta Pisano
Etta Pisano, MD, chief research officer at the American College of Radiology, and the principal investigator of TMIST

The number of women and sites participating is likely to increase rapidly in the months ahead. Etta Pisano, MD, chief research officer at the American College of Radiology, and the principal investigator of TMIST, heads the efforts to get clinics involved.  “We have 15 approved clinics working on the logistics to begin enrollment, and another 34 have committed to joining. We are pleased that there has been a great deal of interest from international sites and expect to bring on additional sites in Europe and Asia in the next 6 months,” Dr. Pisano said.

TMIST is a randomized phase 3 trial comparing standard digital mammography (2-D) with the newer tomosynthesis mammography (3-D). The goal is to follow all participants to see if they are diagnosed with breast cancer or a precancerous condition, and to record their treatment and outcomes from the time of randomization until the end of the study.

TMIST was designed to provide evidence about the role of mammography screening in reducing the incidence of life threatening, advanced breast cancers. This is a stand-in for breast cancer mortality, the usual endpoint for screening trials, because a trial using that endpoint would take many more years to complete.  

All told, 164,946 healthy women ages 45 to 74 who are already planning to get routine mammograms will be enrolled. Women will be randomized to either 3-D or 2-D screening mammograms for 5 years. Each woman is assigned to a screening frequency of every 1 or every 2 years, based on her individual risks for developing breast cancer.

While Medicare and many private insurance programs provide full cost coverage for screening mammograms, with no co-pay, copays are still allowed for some mammograms in some states.  Based on requests from women taking part in TMIST, some states are now funding co-payments or completely covering the participants’ cost for mammograms, according to the American College of Radiology (ACR).  The study also has some funding for uninsured patients subject to the charity care policies of the participating institutions.

States with Laws that Mandate
NO Co-pay for Screening Mammograms
States with Laws that Allow
Co-pays for Screening Mammograms
Arizona, Colorado, Connecticut, Illinois, Kansas, New Hampshire, New Jersey, New York, Oklahoma, Pennsylvania, Texas, Vermont, Washington Kentucky, Louisiana, Maryland, Montana

TMIST is supported by the NCI Community Oncology Research Program (NCORP) and co-led by the ECOG-ACRIN Cancer Research Group. “About 50 million screening mammograms occur every year in the U.S. and it’s important to note that despite the technology disbursement, there is a research study going on to inform the science and the clinical practice,” said NCORP Director Worta McCaskill-Stevens, MD, MS.

Toward Personalized Screening Recommendations

TMIST researchers also are collecting evidence of significant secondary endpoints including false positives, recall rates, biopsy rates, and overdiagnosis. Data is collected on the results of every mammogram, whether the imaging shows no signs of cancer, findings suspicious of cancer, or a breast cancer. Medical follow-ups, such as more imaging or biopsies, also are reported.

Portrait of Worta McCaskill-Stevens
NCORP Director Worta McCaskill-Stevens, MD, MS

“Any increase in sensitivity with a new technology could be of benefit, harm, or a mixture, but only a randomized trial can sort it out,” Dr. McCaskill-Stevens added. “The average-risk woman will need personalized guidance about screening tests to make informed decisions around potential risks and benefits in the future.”

A key component of the trial is a biorepository with detailed clinical annotations. The subsequent molecular characterization of specimens and accompanying demographic information could help advance a personalized approach to screening recommendations that determines mammography use and intervals for each person based on their genetics and individual risk factors for developing breast cancer.

 “The molecular evidence is the first step to personalizing breast cancer screening recommendations,” Dr. McCaskill-Stevens said. “The resulting dataset of clinical images and biospecimens will help us tailor future screening to each woman’s individual risk.”

More information and a list of participating sites is available from NCI and ECOG-ACRIN. For a discussion about the science involved in the study, see the article "Why I choose to play a dual role in TMIST" by Dr. McCaskill-Stevens in The Cancer Letter. "TMIST Trial Aims to Provide Clarity on Breast Cancer Screening Approaches" in the NCI Cancer Currents Blog offers more background on 2-D vs 3-D technology. "Implementing TMIST at Your Site: The UNM Experience" by ECOG-ACRIN shows an example of how a site is implementing the study.


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