Longitudinal Association of Quantitative Background Parenchymal Enhancement with Breast Cancer Risk among Women with BRCA1/2 Pathogenic Variants.

BACKGROUND

Background parenchymal enhancement (BPE) on breast magnetic resonance imaging (MRI) is a potential biomarker for breast cancer risk, but its utility among women with BRCA1/2 pathogenic variants (PV) is unclear.

METHODS

We investigated the longitudinal association of quantitative BPE measures with breast cancer risk among women with BRCA1/2 PVs. Measures included median BPE and the proportion of fibroglandular tissue (FGT) voxels with ≥20% enhancement (BPE20/FGT). The primary outcome was incident breast cancer diagnosed ≥6 months after MRI. Repeated measures proportional hazards models assessed associations of BPE with cancer, adjusting for age, menopausal status, volumetric breast density (VBD), body mass index (BMI), and BRCA type.

RESULTS

Among 385 women-39 of whom developed breast cancer-with 1,278 MRIs, the median age at first MRI was 36 (IQR 30-46) years. The BPE20/FGT ratio was associated with increased risk in both the smaller model (age and menopause adjusted, HR = 1.13, P < 0.005) and the larger model (adjusted for VBD, BMI, and BRCA1 vs. BRCA2, HR = 1.13, P < 0.005, both measures HR per 10 units). The association was stronger in axial MRIs in both models (smaller: HR = 1.26, P < 0.001; larger: HR = 1.34, P < 0.005). Median BPE showed similar results. In a subset of 165 women, a decrease in BPE was observed from the last measurement before oophorectomy to the first after oophorectomy (P < 0.04).

CONCLUSIONS

In this study, higher BPE is associated with increased breast cancer risk in women with BRCA1/2 PVs, and BPE decreases after oophorectomy.

IMPACT: Quantitative BPE may help better evaluate breast cancer risk for women with BRCA1/2 PVs, helping women balance the risks and benefits of risk-reducing interventions.