# TMIST (Tomosynthesis Mammographic Imaging Screening Trial)

Source: https://onco.cc/trials/tmist/  
OnCo record `tmist` (Trial). Data CC BY-NC 4.0, attribute "Data from OnCo (onco.cc)"; commercial use needs a licence.

## TL;DR

The trial that will settle whether 3D mammograms prevent more dangerous cancers than standard 2D ones, or just find more small ones.

## Summary

TMIST (ECOG-ACRIN EA1151) is the only randomised trial comparing tomosynthesis with digital mammography on a clinically meaningful endpoint, the rate of advanced cancers (larger, node-positive, metastatic or aggressive subtypes) over 4.5 years, rather than detection rate. Enrolment of about 108,000 women across North America, Argentina and other countries closed in 2024 after a slow start and a downsized target; the trial also builds a biorepository for risk-based screening research. Observational studies show tomosynthesis finds more cancers with fewer recalls, especially in dense breasts, but whether that translates into fewer advanced cancers is exactly what is unknown.

## Fields

- Kind: Trial
- Status: active
- Last checked: 2026-09-10
- Registry id: NCT03233191
- Phase: 3
- Setting: Women aged 45 to 74 randomised to screening with digital breast tomosynthesis (3D) or standard digital mammography, primary endpoint advanced breast cancer
- Sponsor: ECOG-ACRIN / NCI

## Sources

- ClinicalTrials.gov NCT03233191: https://clinicaltrials.gov/study/NCT03233191
- ECOG-ACRIN: TMIST: https://ecog-acrin.org/clinical-trials/tmist-breast-cancer-screening-trial/

## Connected records

- cancers: [HER2-positive breast cancer](https://onco.cc/cancers/breast-her2-positive/), [HR-positive / HER2-negative breast cancer](https://onco.cc/cancers/breast-hr-positive/), [Triple-negative breast cancer (TNBC)](https://onco.cc/cancers/tnbc/)
- technologies: [Mammography & tomosynthesis](https://onco.cc/technologies/mammography/)
- companies: [ECOG-ACRIN Cancer Research Group](https://onco.cc/companies/ecog-acrin/)
- terms: [Overdiagnosis](https://onco.cc/terms/overdiagnosis/), [Screening](https://onco.cc/terms/screening/)

---
JSON: https://onco.cc/api/v1/entities/tmist.json