Photon-counting computed tomography (PCCT) may provide a viable option for preoperative assessment of breast cancer, according to newly published research comparing PCCT to breast MRI, full-field digital mammography (FFDM) and positron emission tomography/computed tomography (PET/CT).
For the prospective study, recently published in Radiology, researchers reviewed imaging data for 126 women who had BI-RADS 4C or higher presentations on ultrasound or FFDM, and underwent subsequent breast MRI and contrast-enhanced PCCT. The study authors added that 18F-FDG PET/CT was utilized in 19 of the 126 patients in the cohort.
The study authors found good inter-reader agreement between PCCT and breast MRI for lesion characterization (0.69-0.91 vs. 0.75-0.88). For detection of additional lesions, PCCT offered sensitivity that was comparable to breast MRI (65 percent vs. 57 percent) and significantly higher than FFDM (21 percent).
“To our knowledge, this study provides the first systematic evaluation of PCCT in terms of detecting additional lesions, demonstrating a diagnostic performance comparable to that of MRI and a higher sensitivity than that of FFDM. Future investigations could explore whether quantitative spectral or temporal PCCT parameters could further enhance lesion characterization,” noted lead study author Qiuyi Fu, MD, who is affiliated with the Department of Radiology at Ruijin Hospital and the Shanghai Jiao Tong University School of Medicine in Shanghai, China, and colleagues.
Comparing PCCT and MRI for detection of lymph node metastasis, the study authors determined that PCCT offered higher sensitivity (78 percent vs. 69 percent), comparable specificity (88 percent vs. 85 percent) and higher positive predictive value (PPV) (77 percent vs. 69 percent).
“In this study, PCCT provided better nodal assessment results than MRI, likely because of the broader field of view of PCCT, including the axillary, internal mammary, and supraclavicular regions,” added Fu and colleagues.
However, PCCT offered weaker performance than FFDM with detection of suspicious calcifications. While FFDM findings of suspicious calcifications corresponded to 50 out of 54 lesions (92.6 percent), the researchers found that PCCT missed 44 percent of suspicious calcifications detected with FFDM.
Three Key Takeaways
• PCCT rivals MRI for lesion detection and nodal staging. In this 126-patient study, PCCT showed sensitivity for additional lesions comparable to breast MRI (65 percent vs. 57 percent) and far superior to full-field digital mammography (FFDM) (21 percent). For lymph node metastasis, PCCT actually outperformed MRI on sensitivity (78 percent vs. 69 percent) and PPV (77 percent vs. 69 percent), likely due to its wider field of view covering axillary, internal mammary, and supraclavicular regions.
• Calcification detection remains a weak point for PCCT. FFDM still outperforms PCCT for suspicious calcifications. PCCT missed 44 percent of calcifications that FFDM detected. This suggests PCCT shouldn't replace mammography for calcification assessment at least with current reconstruction protocols.
• Clinical validation is still preliminary. BI-RADS criteria aren't yet validated for PCCT and protocol variability (e.g., prone positioning to match MRI) may limit reproducibility across sites. Accordingly, these findings, while promising, need confirmation in larger studies before PCCT can be adopted as a standard preoperative tool in this patient population.
Noting that variability in image reconstruction parameters and smaller sample size may have affected the results with calcifications, the study authors maintained that subsequent studies may provide greater clarity.
“Accurate assessment of microcalcification size and distribution remains challenging, as tomographic CT differs from planar FFDM. Future research should investigate optimized reconstruction algorithms and convolutional neural network–based ultrahigh-resolution enhancement to improve detectability,” posited Fu and colleagues.
(Editor’s note: For related content, see “Can Contrast-Enhanced Mammography Improve Breast Cancer Staging?: Nine Takeaways from a New Literature Review,” “Moving Beyond Mammography for Screening and Staging of Invasive Lobular Carcinoma” and “Current Perspectives on PET/CT Imaging in Patients with Metastatic Breast Cancer.”)
In regard to study limitations, the authors acknowledged that the BI-RADS system is not currently validated for PCCT application. While noting that prone patient positioning was emphasized for PCCT scans in order to match breast MRI scans, they conceded that protocol variations may have an impact on broader applicability across multiple facilities.
