TMIST (Tomosynthesis Mammographic Imaging Screening Trial)

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.