Prostate Cancer Metastatic Sites
Prostate cancer most commonly spreads to bone (90% of metastatic cases), followed by lymph nodes, lungs (46%), liver (25%), pleura (21%), and adrenal glands (13%). 1
Primary Metastatic Pattern: Bone
The skeleton is overwhelmingly the dominant site of prostate cancer metastasis, with bone involvement occurring in 90% of patients who develop distant spread 1. This bone-predominant pattern distinguishes prostate cancer from many other solid tumors.
Unique Spinal Metastatic Pathway
Prostate cancer spreads to bone through two distinct mechanisms:
- Classical hematogenous route via the vena cava to lungs and then systemically 1
- Retrograde venous spread (Batson's plexus) directly from the prostate to the lumbar spine, bypassing the lungs entirely 1
The evidence for this backward venous pathway is compelling: spine metastases occur in smaller tumors (4-6 cm) compared to lung metastases (6-8 cm maximum frequency), suggesting spine involvement precedes lung spread 1. Additionally, there's an inverse relationship between spine and lung metastases, and a gradual decrease in spine involvement from lumbar (97%) to cervical levels (38%), consistent with initial lumbar seeding followed by upward spread 1.
Secondary Metastatic Sites
Lymph Nodes
Regional lymph node involvement occurs in approximately 14% of patients at presentation 2. Nodal metastases are typically assessed with contrast-enhanced CT using ≤5-mm axial slices 3.
Visceral Metastases
Lung metastases occur in approximately 46% of patients with distant spread 1, with prevalence around 7-9% in castration-resistant disease 3. Pulmonary involvement is best detected with chest CT imaging 3.
Liver metastases are present in about 25% of patients with hematogenous spread 1, or approximately 10.2% of all metastatic cases 3. Hepatic involvement can be accurately assessed with CT 3 and, though uncommon, can rarely cause fulminant hepatic failure 4.
Adrenal metastases occur in approximately 13% of patients with distant disease 1 and can be detected on standard imaging studies 3.
Rare Metastatic Sites
While uncommon, prostate cancer can metastasize to the brain, kidneys 4, and even the testis 5. These unusual sites should be considered in patients with known prostate cancer presenting with new masses at these locations 5.
Clinical Subtypes Based on Spread Pattern
The Prostate Cancer Clinical Trials Working Group 3 defines five clinical subtypes 3:
- Locally recurrent disease
- Non-metastatic castration-resistant prostate cancer (rising PSA without detectable imaging findings)
- Nodal spread
- Bone disease
- Visceral disease
The presence of visceral metastases indicates more aggressive disease and poorer prognosis than bone-only metastases 3, with patients having castration-resistant disease and bone metastases showing median survival <2 years 3.
Risk Factors for Bone Metastasis Development
Older age, unmarried status, lymph node involvement, poor Gleason grade, and presence of lung, brain, or liver metastases all increase risk for bone metastasis development 6. Black race and higher T stage also positively correlate with bone metastasis incidence 6.
Imaging Strategy
Bone scintigraphy (potentially with SPECT) remains the standard for detecting bone metastases 3, while contrast-enhanced CT of chest, abdomen, and pelvis is optimal for assessing nodal and visceral spread 3. Understanding the metastatic pattern is both prognostic and should guide imaging strategies 3.