Expert Case Review: The Role of FDG-PET/CT in Diagnosing and Predicting Prognosis in Metastatic Breast Cancer

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Case Review: The Role of FDG-PET/CT in Diagnosing and Predicting Prognosis in Metastatic Breast Cancer

Revisión de caso: El papel de la FDG-PET/CT en el diagnóstico y la predicción del pronóstico del cáncer de mama metastásico

증례 검토: 전이성 유방암 진단 및 예후 예측에 있어서 FDG-PET/CT의 역할

Introduction: The Expanding Role of PET/CT in Breast Cancer Management

Breast cancer is among the most commonly diagnosed malignancies in women worldwide. The clinical trajectory of metastatic breast cancer (MBC), characterized by its poor prognosis and treatment complexity, calls for precise diagnostic and staging tools. While traditional imaging methods such as ultrasound, mammography, and MRI provide detailed anatomical insights, functional imaging via 18F-fluorodeoxyglucose positron emission tomography/computed tomography (FDG-PET/CT) has revolutionized the assessment of disease burden and therapy response. This column discusses a representative clinical case to highlight the diagnostic and prognostic utility of FDG-PET/CT in MBC.

Case Overview: A 44-Year-Old Female with Metastatic Breast Cancer

  • Patient: 44-year-old female

  • Diagnosis: Right breast cancer with ipsilateral axillary lymph node involvement, histologically classified as ductal carcinoma in situ (DCIS)

  • Metastasis: Single osseous lesion in the sacrum identified on PET/CT

  • Imaging Modality: FDG-PET/CT for staging and post-chemotherapy restaging

  • Treatment: Chemotherapy with Taxol and Avastin

  • Outcome: Complete metabolic response (CMR)

Imaging Analysis

Figure 1: Initial Staging FDG-PET/CT Findings
A large, heterogeneous FDG-avid mass is visualized in the right breast (A2), accompanied by multiple hypermetabolic axillary lymph nodes (A1) and a solitary sacral metastasis (A3).
Caption: FDG-PET/CT scan at staging reveals extensive right breast involvement with metastatic lymph nodes and sacral bone metastasis.



Figure 2: Post-Chemotherapy PET/CT Assessment

The follow-up PET/CT demonstrates no residual metabolic activity in previously noted lesions. Diffuse bone marrow uptake is likely reactive post-chemotherapy.
Caption: Complete metabolic response indicating excellent therapeutic efficacy. Bone marrow activation reflects hematologic regeneration.

Clinical Implications

  1. Upstaging via Metastatic Detection PET/CT identified a sacral osseous lesion not visible on prior imaging, which reclassified the patient as stage IV. This upstaging significantly influenced the treatment approach.

  2. Metabolic Response as a Therapeutic Biomarker: PET/CT detected a complete metabolic response post-chemotherapy, substantiating its value in early and accurate treatment evaluation.

  3. Differential Diagnosis of Bone Lesions. High FDG uptake in a solitary bone lesion helped confirm metastatic involvement, ruling out benign skeletal abnormalities.

Research Trends and Evolving Metrics

  • Quantitative PET parameters such as SUVmax, MTV, and TLG are being validated as prognostic markers in breast cancer.

  • Emerging PET tracers targeting immune checkpoints like PD-L1 are under investigation for precision immunotherapy.

  • Integration of radiomics and AI is expanding PET imaging's role in personalized oncology.

Expert Quiz Section

  1. Which lesion led to disease upstaging in this case?
    Answer: Sacral metastasis
    Explanation: This lesion confirmed distant spread, shifting staging to IV.

  2. What does CMR signify on PET/CT?
    Answer: Complete metabolic response
    Explanation: No detectable FDG activity in known disease sites.

  3. What could increased bone marrow uptake post-therapy indicate?
    Answer: Reactive hematopoietic response
    Explanation: Often seen after chemotherapy as a benign finding.

  4. Why is PET/CT superior to CT in therapy monitoring?
    Answer: Functional changes precede structural changes
    Explanation: PET detects early metabolic shifts before morphological alterations.

  5. Which parameter is NOT commonly used in PET prognostics?
    A. SUVmax
    B. MTV
    C. TLG
    D. Hounsfield Unit (HU)
    Answer: D. HU
    Explanation: HU is a CT-based metric and not part of PET quantification.

References (IEEE Format)

[1] A. Groheux et al., "18F-FDG PET/CT in staging and restaging of breast cancer," J Nucl Med, vol. 57, no. S1, pp. 17S–26S, 2016.
[2] K. M. Avril et al., "Metabolic characterization of breast tumors with PET," J Clin Oncol, vol. 24, no. 5, pp. 743–749, 2006.
[3] K. C. Osborne et al., "FDG PET/CT in metastatic breast cancer," Eur J Nucl Med Mol Imaging, vol. 46, pp. 210–219, 2019.
[4] J. Y. Lee et al., "Predictive value of FDG PET/CT in neoadjuvant chemotherapy," Breast Cancer Res Treat, vol. 170, pp. 275–283, 2018.
[5] A. S. Wu et al., "Radiomics in breast cancer PET," Mol Imaging Biol, vol. 23, pp. 173–183, 2021.
[6] S. Choi et al., "PET/CT predicts survival in metastatic breast cancer," Am J Clin Oncol, vol. 44, pp. 413–419, 2021.
[7] Y. H. Paeng et al., "PET and MRI in therapy response," Korean J Radiol, vol. 20, no. 5, pp. 671–680, 2019.

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