Mammograms miss some breast cancers in women with average breast density, and a new study will test whether a faster, cheaper MRI scan can find them. Around 40% of women aged 50–52 have average-density breasts (category B), yet most supplemental screening trials focus only on women with very dense tissue. This leaves a gap: no one knows whether these women could also benefit from additional imaging. The DYAMOND study will recruit 1,000 women in this group, offer them a FAST MRI after their first NHS mammogram, and count how many extra cancers the MRI detects. If it finds at least 4 additional cancers per 1,000 women, the results will inform the design of a future randomised trial. Success could shift NHS breast screening policy to include average-density women in supplemental MRI programmes, catching aggressive cancers—such as lobular carcinoma and small grade 3 tumours—that mammography routinely misses. Earlier detection would reduce late-stage diagnoses and improve survival, without requiring every woman to undergo a full-length MRI scan.
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Research question For women with average breast density, can FAST MRI detect sufficient breast cancers, missed at first screening mammogram, to justify this group’s inclusion in a future FAST MRI screening programme within the NHS Breast Screening Programme (NHSBSP)? Background To reduce breast cancer mortality, we need a cost-effective screening tool that will preferentially detect the aggressive cancers that are not well seen on mammograms. Recently, research teams worldwide have focussed on offering supplemental/additional imaging (e.g. with FAST MRI) only for the subset of women with high mammographic density. However, women with average mammographic density, category B by American College of Radiologists criteria, can also have their cancers missed by mammography because mammograms are not good at showing lobular carcinoma or small grade 3 aggressive cancers. Aims and objectives To determine the number of additional cancers detected by FAST MRI (missed by standard screening mammography) in the average density group in order to refine the design and define the study population for a future randomised controlled trial of FAST MRI. Methods Prospective, multicentre diagnostic yield, single arm study with internal pilot (for recruitment etc.). We will screen women invited for their first mammogram with NHSBSP (age 50-52) to identify those with average mammographic density (category B). We chose this study population (40% of the screened population) because they are excluded from other supplemental screening trials despite a knowledge gap about whether supplemental screening could benefit them. This diagnostic yield study will offer these women supplemental FAST MRI. The primary outcome is the number of cancers missed by mammography but detected by FAST MRI. Secondary outcomes include the grades, sizes and stages of cancers detected, recruitment rates, recall rates, biopsy rates, any adverse reactions to FAST MRI and intervention acceptability to participants. A sample of 1000 women will be recruited to test whether FAST MRI could detect at least 4 additional cancers per 1000 women screened. With a target detection rate of 11 additional cancers per 1000, 80% power, 5% one-sided significance level and using a Fleming’s two-stage design, a minimum of 959 women would be required with 381 women accrued during the first stage. Timelines for delivery 42 months grant (May 2023 - Oct 2026) with 7 months setup; 15 months recruitment, 12 months for early call FAST MRI at 1 year and 8 months for analysis and write up. Impact and Dissemination If this study shows that FAST MRI detects sufficient cancers missed by mammography for women with average mammographic density, a more inclusive approach will be taken in future breast screening trials to include the 40% of women with category B breasts. If the subsequent RCT confirms effectiveness and cost effectiveness for screening with FAST MRI, the potential benefit to women would be huge. Breast cancers that would otherwise be missed by mammography will be detected earlier by FAST MRI and lives will be saved. We will send a summary of results to the UK National Screening Committee, Director of Screening (Dept. of Health and Social Care), key members of NHS England, and the NHSBSP. Members of the public and patients will help ensure that findings are written in an accessible way and shared with their networks. We will publish the results in academic journals and present them at medical meetings.
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