When should a patient with a malignant neoplasm (cancer) of the breast undergo a Positron Emission Tomography (PET) scan routinely?

PET Scan Recommendations for Breast Cancer Patients

PET scans should not be used routinely for breast cancer patients but are recommended only in specific clinical scenarios such as locally advanced disease (stage IIB and higher), when conventional imaging is equivocal, or for suspected recurrence. 1

Appropriate Indications for PET Scans in Breast Cancer

Initial Staging

• Stage I (T1, N0, M0): PET scan is NOT recommended 1

  • Limited spatial resolution (5-6mm) makes PET inferior to sentinel node biopsy
  • Low risk of distant metastases in T1N0 disease
  • High rate of false positives (3.0%) compared to true positives (0.9%) 1

• Stage IIA: Generally NOT recommended routinely 1

  • Only 0.8-4.5% detection rate of distant disease in most studies
  • Consider only if large T2 tumors (>3cm) 1

• Stage IIB and higher: PET scan IS recommended 1

  • Detection of distant metastases in 9.8-15% of stage IIB patients
  • Can replace conventional imaging (bone scan, chest X-ray/CT, abdominal US/CT) 1
  • More cost-effective with lower radiation dose (14mSv vs 21mSv) 1
  • Reduces false positives by 50% compared to conventional imaging 1

• Stage III (including inflammatory breast cancer): PET scan IS recommended 1

  • Can detect additional nodal metastases in 23% and distant metastases in 14% of patients 1
  • Valuable for radiation therapy planning 1

Special Circumstances

• When conventional imaging is equivocal or suspicious 1
• For suspected recurrence with elevated tumor markers or symptoms 1, 2
• For monitoring response to therapy in locally advanced disease 2

Limitations and Pitfalls of PET Scanning

False Negatives

• Small lesions ≤10mm 1
• Low-grade tumors 1
• Certain histologic subtypes (lobular, tubular, DCIS) 1, 3
• Recent or ongoing therapy 1

False Positives

• Inflammatory processes (infection, trauma, recent surgery) 1
• Post-treatment inflammation 1
• Physiologic uptake (brown fat, bone marrow, myocardium) 1

Recommendations Based on Symptoms/Findings

Instead of routine PET scanning, the NCCN recommends targeted imaging based on specific findings:

• Localized bone pain or elevated alkaline phosphatase: Bone scan 1, 4
• Abnormal liver function tests, abdominal symptoms, or abnormal abdominal exam: Abdominal imaging (US, CT, or MRI) 1, 4
• Pulmonary symptoms: Chest diagnostic CT 1

Reporting and Interpretation

• PET scans should be reported according to PERCIST or EORTC PET response criteria 1
• Quantitative features (SUVmax, MATV/MTV, TLG) provide valuable prognostic information 1
• For patients on immunotherapy, special reporting considerations apply 1

Key Practice Points

• PET scanning is not cost-effective or clinically beneficial for routine surveillance in asymptomatic patients 1
• PET can provide valuable information about disease extent in locally advanced disease, potentially altering treatment decisions 5, 2
• When used appropriately, PET can reduce unnecessary biopsies and procedures by clarifying equivocal findings from conventional imaging 1
• Newer PET tracers like 18F-FES (for ER status) and 18F-NaF (for bone metastases) may have specific roles in selected patients 2, 6

Remember that inappropriate use of PET scanning in early-stage disease can lead to false positives, unnecessary additional procedures, treatment delays, and increased healthcare costs without improving patient outcomes.