Clinical Report: FAPI PET/CT Identifies Hidden Contralateral DCIS

Overview

This case study demonstrates the superior sensitivity of FAPI PET/CT over traditional FDG PET/CT in detecting low-metabolic malignancies, such as DCIS, and accurately staging regional nodal involvement in a patient with synchronous bilateral breast cancer. FAPI PET/CT significantly altered the clinical management and treatment response monitoring.

Background

Accurate staging in breast cancer is crucial for effective management and treatment planning. Traditional imaging methods, like FDG PET/CT, may miss low-glucose metabolizing tumors and small metastases, leading to potential under-staging. The introduction of FAPI PET/CT offers a promising alternative by targeting cancer-associated fibroblasts, potentially improving diagnostic accuracy.

Data Highlights

Key Findings

• FAPI PET/CT identified a contralateral DCIS that was missed by FDG PET/CT.
• FAPI PET/CT revealed occult metastases in the left axillary and supraclavicular lymph nodes.
• Post-neoadjuvant therapy, FAPI PET/CT showed a drop in uptake, indicating a complete response.
• FAPI PET/CT provides higher sensitivity for low-metabolic malignancies compared to FDG PET/CT.
• Accurate staging with FAPI PET/CT can significantly influence treatment decisions in breast cancer management.

Clinical Implications

The findings suggest that FAPI PET/CT could be integrated into clinical practice for improved staging and monitoring of breast cancer, particularly in cases where FDG PET/CT may be insufficient. This could lead to more tailored treatment strategies and better patient outcomes.

Conclusion

FAPI PET/CT demonstrates enhanced sensitivity in detecting low-metabolic breast cancer lesions, which is critical for accurate staging and effective treatment planning. Its role in clinical decision-making warrants further investigation.

References

1. Hao et al, ASCO Post, 2024 -- FAPI PET/CT May Improve Staging in Newly Diagnosed Breast Cancer
2. Springer, 2025 -- Imaging Findings Indicating Pectoral Nerve Involvement in Perineural Metastasis of Breast Cancer to the Brachial Plexus
3. The ASCO Post, 2025 -- Identification of FAP-Expressing Tumors With Radiotracer
4. ScienceDirect, 2024 -- Early breast cancer: ESMO Clinical Practice Guideline for diagnosis, treatment and follow-up
5. Journal of Nuclear Medicine, 2024 -- SNMMI Procedure Standard/EANM Practice Guideline for Fibroblast Activation Protein (FAP) PET
6. The ASCO Post — Molecular Imaging May Improve the Staging and Treatment of Pancreatic Ductal Adenocarcinoma
7. Early breast cancer: ESMO Clinical Practice Guideline for diagnosis, treatment and follow-up - ScienceDirect
8. SNMMI Procedure Standard/EANM Practice Guideline for Fibroblast Activation Protein (FAP) PET | Journal of Nuclear Medicine