Where does breast cancer typically metastasize to?

Common Sites of Breast Cancer Metastasis

Bone is the most common site of breast cancer metastasis (51%), followed by liver/soft tissue (19%), pleura (16%), lung (14%), and brain (4%). 1

Metastatic Patterns by Molecular Subtype

Different breast cancer subtypes show distinct patterns of metastatic spread:

• Luminal cancers (ER/PR positive):

  • Primarily metastasize to bone 1, 2
  • 82% of patients who develop bone metastases have either ER and PR or ER positivity in the primary tumor 1
  • Up to 70% of women with stage IV disease have bone metastasis 1
  • Carry long-term risk of recurrence, especially to bone 1

• HER2-enriched cancers:

  • Preferentially spread to liver and lung 1, 2
  • Higher rate of recurrence in the first 4 years 1

• Triple-negative/basal-like cancers:

  • Commonly metastasize to liver and brain 1, 2, 3
  • Higher rate of recurrence in the first 4 years 1
  • The predilection for bone metastases does not apply to basal-like tumors 1

Invasive Lobular Carcinoma (ILC) vs. Invasive Ductal Carcinoma (IDC)

• ILC has unique metastatic patterns:

  • More likely to spread to gastrointestinal tract, peritoneum, and retroperitoneum 4
  • Can present with unusual symptoms like jaundice, anemia, or rectal bleeding 4
  • PET/CT has limited sensitivity for detecting ILC metastases 1

• IDC follows the more typical metastatic pattern to bone, lung, liver, and brain 4

Prognostic Implications

• Liver metastases are associated with the worst prognosis (median survival of only one month after diagnosis) 5
• Brain metastases have a median survival of three months after diagnosis 5
• Bone and lung metastases have a median survival of 12 months after diagnosis 5
• Multiple metastatic sites have a median survival of 7.5 months 5

Clinical Considerations

• Up to 13.6% of women diagnosed with early-stage breast cancer will develop bone metastasis within 15 years of diagnosis, even if the primary tumor is low grade 1

• Metastatic disease can present in unusual ways, including:

  • Acute appendicitis 6
  • Small bowel obstruction 6
  • Gastric metastasis 7

• The 5-year survival rate for stage 4 (metastatic) breast cancer is approximately 25%, though this varies significantly based on cancer subtype and metastatic sites 2

Imaging Considerations

• Tc-99m bone scans have 98% sensitivity for detecting early bone metastasis in symptomatic patients 1
• PET/CT has higher sensitivity and specificity (97% and 91%, respectively) for detecting distant metastases compared to conventional imaging (86% and 67%) 1

Understanding the typical patterns of metastatic spread based on breast cancer subtype is crucial for early detection and appropriate management of metastatic disease, which can significantly impact patient outcomes and quality of life.