Abstract PS1-06-13: The Utility of DWIBS for Breast Cancer Screening: A Promising Alternative to Mammography

Abstract Background and Objectives: Diffusion-weighted whole-body imaging with background suppression (DWIBS) is a non-contrast MRI technique that visualizes the diffusion of water molecules while suppressing background signals, enabling the detection of malignant lesions. Due to its non-invasive nature and absence of radiation exposure, DWIBS has recently attracted increasing attention as a promising modality for breast cancer screening in Japan.Notably, no Japanese population-based data have demonstrated a mortality reduction from mammographic screening, and the utility of mammography remains a subject of debate, especially given that over 50% of Japanese women have heterogeneously or extremely dense breasts.This study aimed to assess the potential role of DWIBS as an alternative screening tool for breast cancer. Methods: We retrospectively analyzed 710 women who underwent DWIBS-based breast cancer screening at a dedicated MRI screening clinic in Yokohama, Japan, between April 2022 and January 2025. For those referred for further evaluation, clinical and mammographic data, including BI-RADS classification and breast density, were reviewed. DWIBS screening in this study was conducted as a self-paid service at a dedicated MRI screening clinic equipped with advanced diffusion-weighted imaging protocols. All scans were interpreted by radiologists with expertise in breast MRI. Results: Among the 710 women screened by DWIBS, 41 were referred for further evaluation (recall rate: 5.77%; national average for population-based mammographic screening in Japan: 8.4%). Of these, 30 underwent diagnostic work-up (follow-up rate: 73.2%; national average: 90.1%). Breast cancer was diagnosed in 7 individuals, yielding a cancer detection rate (CDR) of 0.99% (national average: 0.33%) and a positive predictive value (PPV) of 17.1% (national average: 5.4%).The median age of those requiring further evaluation was 46.5 years, with 18 of the 41 individuals (43.9%) under the age of 40, which is below the starting age for population-based breast cancer screening in Japan. Among the 7 diagnosed cases, 5 had a family history of breast or ovarian cancer in second-degree relatives, and 2 were under 40 years old with no prior history of mammography.Notably, 3 of the 7 confirmed cancer cases had BI-RADS 1 findings on mammography, indicating false-negative results. In addition, 5 individuals had extremely dense or heterogeneously dense breast tissue. Among the 11 individuals who did not undergo diagnostic follow-up despite referral, potential contributing factors included scheduling challenges, financial constraints, or limited awareness of the need for further evaluation. However, these factors were not formally investigated. Conclusion: DWIBS demonstrated a higher CDR and PPV than mammography and, with additional advantages such as being radiation-free, painless, and free from embarrassment, may serve as a promising tool for breast cancer detection, including among women at high risk or with dense breast tissue. To fully realize its potential as a screening modality, strategies to ensure diagnostic follow-up and further prospective validation are warranted. Citation Format: N. Komatsu, T. Takahara, H. Yano, M. Matsuyanagi, M. Oshi, H. Ideguchi, K. Taruno, N. Hayashi, T. Chishima. The Utility of DWIBS for Breast Cancer Screening: A Promising Alternative to Mammography abstract. In: Proceedings of the San Antonio Breast Cancer Symposium 2025; 2025 Dec 9-12; San Antonio, TX. Philadelphia (PA): AACR; Clin Cancer Res 2026;32(4 Suppl):Abstract nr PS1-06-13.