Where does prostate cancer commonly metastasize to in the body?

Common Sites of Prostate Cancer Metastasis

Prostate cancer most commonly metastasizes to bone, followed by lymph nodes, lungs, and liver, with other visceral sites being less common. 1, 2

Primary Metastatic Sites

• Bone metastases are the most prevalent site of prostate cancer spread, with over 90% of patients with castration-resistant prostate cancer (CRPC) developing bone metastases 2, 3
• Lymph nodes are a common site of metastasis, with disease classified as locoregional (pelvic) or metastatic (extrapelvic, including retroperitoneal, mediastinal, and thoracic) 1
• Lung metastases occur in approximately 9.1% of metastatic prostate cancer patients, with a prevalence of about 7% in CRPC trials 1, 2
• Liver metastases are present in about 10.2% of metastatic cases 2
• Adrenal glands can also be affected, though less commonly 1, 2
• CNS involvement is rare but can occur in advanced disease 1

Clinical Patterns of Spread

The Prostate Cancer Clinical Trials Working Group 3 (PCWG3) defines five clinical subtypes based on pattern of spread 1:

1. Locally recurrent disease (in prostate/prostate bed)
2. Non-metastatic castration-resistant prostate cancer
3. Nodal spread (pelvic and/or extrapelvic)
4. Bone disease with or without nodal involvement
5. Visceral disease with or without spread to other sites

Imaging Considerations for Detecting Metastases

• Bone metastases are best detected using bone scintigraphy, which may include SPECT for improved characterization 2, 3
• Nodal and visceral metastases are typically assessed with contrast-enhanced CT scan of chest, abdomen, and pelvis using ≤5-mm axial slices 1, 2
• Chest CT imaging is recommended for detection of lung metastases due to their relatively frequent occurrence in CRPC 1
• Liver metastases are evaluated using CT, which provides accurate assessment of hepatic involvement 2

Clinical Implications and Prognosis

• The presence of visceral metastases generally indicates more aggressive disease and poorer prognosis than bone-only metastases 2
• Patients with CRPC and bone metastases have a median survival of less than 2 years 2
• Understanding the pattern of metastatic spread is prognostic and should guide imaging strategies and treatment decisions 1, 2

Rare Metastatic Sites

While uncommon, prostate cancer can occasionally metastasize to atypical locations:

• Gastrointestinal tract (stomach, rectum) 4
• Renal pelvis and ureter 5
• Paravertebral regions 6
• Orbital tissues 7

Monitoring Considerations

• Bone metastases may paradoxically appear worse on imaging despite effective treatment (flare phenomenon), which can lead to false interpretation of disease progression 2, 3
• PSA may not be a reliable marker of disease status in patients on androgen deprivation therapy, making imaging crucial for monitoring 3
• For patients with known metastatic disease, follow-up imaging should include assessment of all previously identified sites of disease 2

Molecular Mechanisms

The predilection of prostate cancer for bone metastasis involves complex cellular interactions within the bone microenvironment, creating a cycle of bone destruction and tumor growth 8. Understanding these mechanisms has led to the development of bone-targeted therapies that can help manage skeletal-related events in patients with bone metastases 2.