Prostate Adenocarcinoma — PSA 22, Iliac Lymph Node Metastasis

Staging & Classification

• PSA 22 ng/mL → High-risk by definition (PSA >20 ng/mL alone qualifies as high-risk regardless of Gleason score or T stage)
• Iliac lymph node metastasis: The common iliac lymph nodes are considered distant metastases (M1a) under AJCC 8th edition TNM staging; obturator, external/internal iliac, and presacral nodes are "regional" (N1), but common iliac nodes are classified as M1a (non-regional nodal mets). If only internal/external iliac nodes are involved → cN1 M0. If common iliac → M1a.

This distinction has critical management implications — clarify which iliac nodes are involved on imaging. — Harrison's Principles of Internal Medicine 22E; Campbell-Walsh-Wein Urology

Workup / Staging Investigations

PSMA PET imaging has "radically altered" the assessment of prostate cancer spread and is now state-of-the-art for Gleason grade group ≥3 (Harrison's, 2025). Sensitivity for LN detection is ~40–50% (cannot detect <2 mm foci), but specificity ~95%.

Treatment Options

cN1 M0 (iliac nodes = regional pelvic nodes)

• Radical prostatectomy (RP) + extended pelvic lymph node dissection (ePLND)
  • RP is not abandoned even if LN involvement found intraoperatively — prospective data show survival benefit over abandoning surgery
  • ePLND template: external iliac vessels, obturator fossa, internal iliac artery territory
• Followed by adjuvant ADT ± pelvic EBRT

• EBRT to prostate ± pelvic lymph nodes + long-term ADT (2–3 years)
• This is the most commonly used approach for cN1 disease when surgery is not preferred
• Landmark data (STAMPEDE, GETUG-AFU 15) support the addition of docetaxel or abiraterone to ADT for high-volume/high-risk disease

• For patients not suitable for local therapy due to tumor burden, comorbidity, or patient preference

If M1a (common iliac nodes = distant mets)

Key Management Principles

1. Castration (ADT initiation): Start immediately — LHRH agonist (risk of testosterone flare → cover with antiandrogen for first 4 weeks) or LHRH antagonist (degarelix — no flare, may reduce cardiovascular events)
2. Local therapy: Even in M1a oligometastatic disease, adding radiation to the primary prostate tumor improves outcomes (STAMPEDE metastasis-directed therapy data — benefit mainly in low-burden metastatic disease)
3. Bone protection: Start zoledronic acid or denosumab early to prevent skeletal-related events
4. Germline testing: BRCA2 mutations (present in ~6%) alter prognosis and qualify for PARP inhibitor combinations
5. MSI/MMR testing: ~3% tumors MSI-high → pembrolizumab eligible
6. PSA monitoring: Response to castration predicts outcomes; PSA nadir at 7 months is a key prognostic milestone

Prognosis

• PSA 22 + N1/M1a: 5-year OS has improved substantially with triplet/doublet therapy — was historically ~30% for distant metastatic disease but contemporary mHSPC combination regimens have significantly extended median OS (>5 years in low-volume, ~3–4 years in high-volume disease with combination treatment)
• PSADT after treatment initiation is the most important dynamic prognostic marker

Summary Management Algorithm

PSA 22 + Iliac LN mets
        ↓
Confirm node territory (pelvic vs. common iliac)
        ↓
PSMA PET/CT + mpMRI + bone survey + Gleason grading
        ↓
    cN1 M0                          M1a (or M1b with bone)
       ↓                                    ↓
RP + ePLND + adjuvant ADT         ADT + NHA (abi/enza/apa)
   OR                               ± Docetaxel (fit, high-volume)
EBRT + 2-3yr ADT                   ± Prostate RT (low metastatic burden)
       ↓                                    ↓
   Monitor PSA                       Bone protection + germline testing

• Harrison's Principles of Internal Medicine 22E (2025, McGraw Hill), Chapter 92
• Campbell-Walsh-Wein Urology, Chapters on prostate cancer imaging and management
• EAU-EANM-ESTRO-ESUR-ISUP-SIOG Guidelines on Prostate Cancer 2024, Sections 4, 6.3
• STAMPEDE, LATITUDE, ENZAMET, ARASENS trials