But they aren't really sure about the 2 pelvic nodes. They are indeterminate. I know they listed it as N1, but the...

This is an excellent and clinically critical question - the distinction between N0 and N1 disease fundamentally changes the treatment paradigm, and you're right to seek clarity before committing to a more intensive treatment approach.

Understanding "Indeterminate" Nodal Status

Your father's situation represents a common diagnostic dilemma:

• MRI: No lymph node enlargement (size criteria: typically >8-10mm short axis considered abnormal)
• PET/CT: Low-level uptake in 2 right pelvic nodes
• Clinical staging: Provisionally labeled N1, but uncertainty remains

Key Question: What type of PET tracer was used?

This is critical for interpretation:

PSMA PET/CT (68Ga-PSMA-11 or 18F-DCFPyL):

• SUVmax thresholds: Nodes with SUVmax >2.5-3.0 are typically considered suspicious, but no absolute cutoff
• Sensitivity/Specificity: ~40% sensitivity, ~95% specificity for pelvic nodes (per NCCN)
• False positives: Inflammatory nodes, benign prostatic hyperplasia spillover
• False negatives: Micrometastases <2-3mm, low PSMA-expressing variants

Conventional PET/CT (18F-FDG or 18F-Fluciclovine):

• Lower specificity for prostate cancer nodal metastases
• FDG: Poor performance in prostate cancer (low metabolic activity in many cases)
• Fluciclovine: Better than FDG but inferior to PSMA PET

Critical point: "Low-level uptake" on PSMA PET in normal-sized nodes is equivocal - could represent:

1. True micrometastases
2. Reactive/inflammatory changes
3. Technical artifact or background activity

Diagnostic Strategies to Resolve N0 vs. N1 Uncertainty

1. Advanced Imaging Refinement

A. Repeat PSMA PET/CT with Quantitative Analysis

• If initial scan was conventional imaging, PSMA PET is essential (NCCN Category 1 recommendation for high-risk disease)
• Request SUVmax values for the suspicious nodes
• Compare nodal SUVmax to:
  • Primary tumor SUVmax (ratio <0.5 suggests benign)
  • Liver background SUVmax (nodes <2× liver background often benign)
  • Contralateral normal nodes

B. Multiparametric MRI (mpMRI) with Diffusion-Weighted Imaging (DWI)

• DWI/ADC mapping: Metastatic nodes show restricted diffusion (low ADC values, typically <1.0 × 10⁻³ mm²/s)
• Size + functional criteria: Combination improves specificity
• Limitation: Cannot definitively rule in/out micrometastases in normal-sized nodes

C. PSMA PET/MRI Fusion (if available at academic center)

• Combines metabolic (PSMA) and anatomic/functional (MRI) data
• May improve characterization of equivocal nodes

2. Pathologic Confirmation (Gold Standard)

A. Image-Guided Lymph Node Biopsy

This is the definitive approach to resolve uncertainty:

Techniques:

• CT-guided percutaneous biopsy: For accessible pelvic nodes >8-10mm
• Transrectal ultrasound (TRUS)-guided biopsy: For nodes near prostate
• Endoscopic ultrasound (EUS)-guided FNA: For deep pelvic/retroperitoneal nodes

Considerations:

• Feasibility: Depends on node size (typically need ≥8-10mm for safe biopsy), location, and patient anatomy
• Yield: Lower for small nodes (<10mm) - may get insufficient tissue
• Risks: Bleeding, infection, nerve injury (rare but possible in pelvis)
• Immunohistochemistry: Can confirm prostatic origin (PSA+, NKX3.1+, PSMA+)

When to pursue:

• If nodes are ≥10mm on any imaging modality
• If treatment decision critically hinges on N0 vs. N1 distinction
• If patient/family strongly prefer pathologic confirmation before intensifying therapy

B. Surgical Staging: Extended Pelvic Lymph Node Dissection (ePLND)

Approach:

• Performed at time of radical prostatectomy (if surgery is being considered)
• Template: Obturator, internal iliac, external iliac, common iliac nodes bilaterally
• Yield: Removes ~20-30 nodes for pathologic examination
• Sensitivity: Detects nodal metastases in ~10-20% of high-risk patients with negative conventional imaging

Considerations for your father:

• NCCN recommendation: ePLND indicated for patients with >2% risk of nodal involvement (Roach formula or nomograms)
• His risk: With cT2a, GS 4+3=7, iPSA 8.35, estimated nodal risk is ~10-15% (warrants ePLND if surgery pursued)
• Caveat: If nodes are truly positive, surgery alone is insufficient - would still require systemic therapy + RT
• Current paradigm shift: Radical prostatectomy for N1 disease is not standard of care (NCCN does not recommend surgery as primary treatment for known N1)

3. Molecular/Genomic Risk Stratification

Decipher Genomic Classifier (already ordered - excellent):

What it provides:

• Genomic risk score (0-1 scale): Predicts metastatic potential independent of clinical factors
• Risk categories: Low (<0.45), Intermediate (0.45-0.6), High (>0.6)
• Metastasis probability: Estimates 10-year risk of distant metastasis
• Biological pathways: Androgen receptor activity, cell cycle progression, immune response

How it helps with N0 vs. N1 uncertainty:

• High Decipher score (>0.6) + equivocal nodes → higher probability nodes are truly positive; supports treating as N1
• Low Decipher score (<0.45) + equivocal nodes → lower probability of nodal involvement; may support N0 treatment approach with close surveillance
• Limitation: Decipher predicts metastatic risk but doesn't directly confirm current nodal status

Complementary Genomic Tests:

• Prolaris (cell cycle progression score): Predicts aggressive biology
• Oncotype DX Prostate: Predicts adverse pathology and metastasis risk
• FoundationOne CDx (somatic tumor sequencing): Identifies actionable mutations, TMB, MSI status

4. Clinical Risk Calculators and Nomograms

Memorial Sloan Kettering (MSK) Nomograms:

• Preoperative nomogram: Predicts probability of lymph node involvement based on PSA, Gleason score, clinical stage, % positive cores
• Input his data: cT2a, GS 4+3, PSA 8.35, biopsy details (% positive cores, % Gleason 4 pattern)
• Output: Estimated probability of N1 disease (if <5%, very low risk; if >15%, high risk)

Roach Formula (simplified):

• Risk of LN involvement = 2/3 × PSA + [(Gleason score - 6) × 10]
• For your father: 2/3 × 8.35 + [(7-6) × 10] = 5.6 + 10 = 15.6% risk
• Interpretation: Intermediate-high risk of nodal involvement, supports ePLND if surgery considered

Partin Tables (Johns Hopkins):

• Predict pathologic stage based on clinical parameters
• Can estimate lymph node involvement probability

5. Observational Approach with Early Restaging

Strategy:

• Initiate ADT alone (without