Is a Positron Emission Tomography (PET) scan indicated when a biopsy is positive for breast cancer?

PET Scan Use in Breast Cancer After Positive Biopsy

PET scans are not routinely indicated for patients with early-stage breast cancer (stages I-II) after a positive biopsy, but may be considered in specific clinical scenarios such as locally advanced disease (stage III) or when there are signs or symptoms of metastatic disease.

When PET Scan is NOT Indicated

• Routine PET/CT scanning is not indicated in the staging of clinical stage I, II, or operable stage III (T3N1M0) breast cancer 1
• PET has limitations including high false-negative rates for small lesions (<1 cm), low-grade tumors, and limited sensitivity for axillary nodal metastases 1
• For early-stage breast cancer (stages I-II), conventional imaging is sufficient in the absence of symptoms suggesting metastatic disease 1

When PET Scan Should Be Considered

Locally Advanced Disease (Stage III)

• For patients with clinical stage III breast cancer, systemic staging with PET/CT may be considered (category 2B recommendation) 1
• PET/CT is particularly useful when standard imaging results are equivocal or suspicious, especially in locally advanced disease 1
• PET/CT can detect regional node involvement and distant metastases in locally advanced breast cancer, including T3N1M0 disease 1

Signs or Symptoms of Metastatic Disease

• PET/CT is recommended for patients with signs or symptoms suggestive of metastatic disease (Level I evidence, 100% consensus) 1
• PET/CT should be considered in patients with rising serum tumor markers (Level II evidence) 1
• PET/CT has high diagnostic accuracy for detecting recurrence with sensitivity, specificity, and area under the ROC curve of 1.00,0.88, and 0.98, respectively 1

Other Specific Indications

• PET/CT can be used to guide the site of biopsy in suspicious cases 1
• PET/CT can improve radiation therapy planning in select cases 1
• PET/CT can substitute for CT and/or bone scan in the detection of bone metastases (Level II evidence, 100% consensus) 1

Advantages of PET/CT in Appropriate Cases

• For distant recurrence detection, PET/CT has shown an area under the ROC curve of 0.99 compared to 0.84 for contrast-enhanced CT and 0.86 for the combination of CT and bone scan 1
• PET/CT can detect bone metastases earlier than conventional imaging, with lesion-based sensitivity comparable to the combination of bone scan and low-dose CT (98.2% vs. 98.6%) 1
• In locally advanced breast cancer, PET/CT has been shown to upstage disease in 48.1% of patients compared to conventional imaging 2

Clinical Decision Algorithm

1. Determine the clinical stage of breast cancer after positive biopsy

   • For stage I-II disease without symptoms → No PET scan needed 1
   • For stage III disease → Consider PET/CT (category 2B) 1

2. Assess for signs/symptoms of metastatic disease

   • If present (bone pain, abnormal liver function tests, etc.) → PET/CT recommended 1
   • If absent → Follow standard imaging protocols 1

3. Consider PET/CT when:

   • Standard imaging results are equivocal or suspicious 1
   • Planning treatment for locally advanced disease 1
   • Guiding biopsy of suspicious lesions 1

Important Caveats

• If PET/CT is performed and clearly indicates bone metastases, a separate bone scan may not be needed 1
• Equivocal or suspicious sites identified by PET/CT should be biopsied for confirmation whenever possible 1
• False positives can occur with PET imaging, including with inflammatory conditions like tuberculosis 3
• The radiation exposure from diagnostic CT component of PET/CT is often greater than from the PET component 1