What is the TNM (Tumor, Node, Metastasis) staging system for prostate cancer?

Prostate Cancer TNM Staging System

The TNM (Tumor, Node, Metastasis) staging system sponsored by the American Joint Committee on Cancer (AJCC) and Union Internationale Contre le Cancer (UICC) is the standard classification system for prostate cancer, systematically describing the anatomical extent of disease based on primary tumor characteristics (T), regional lymph node involvement (N), and distant metastasis (M). 1

T Classification (Primary Tumor)

The T stage describes the size and extent of the primary tumor 1:

• T1: Clinically inapparent tumor not palpable or visible by imaging 1

  • T1a: Tumor incidental histologic finding in ≤5% of resected tissue 2
  • T1b: Tumor incidental histologic finding in >5% of resected tissue 2
  • T1c: Tumor identified by needle biopsy due to elevated PSA (most common clinical stage) 1

• T2: Tumor confined within the prostate 1

  • T2a: Tumor involves one-half of one lobe or less 3
  • T2b: Tumor involves more than one-half of one lobe but not both lobes 3
  • T2c: Tumor involves both lobes 3

• T3: Tumor extends through the prostate capsule (extraprostatic extension) 1

  • T3a: Extraprostatic extension (unilateral or bilateral) 4
  • T3b: Tumor invades seminal vesicle(s) - associated with only 25% biochemical progression-free survival at 10 years 1

• T4: Tumor is fixed or invades adjacent structures other than seminal vesicles (bladder neck, external sphincter, rectum, levator muscles, pelvic wall) 1

N Classification (Regional Lymph Nodes)

Regional lymph nodes include pelvic nodes below the bifurcation of the common iliac arteries 2:

• NX: Regional lymph nodes cannot be assessed 3
• N0: No regional lymph node metastasis 3
• N1: Metastasis in regional lymph node(s) - pelvic lymph node involvement can only be reliably assessed by laparoscopic biopsy or open surgery, as no reliable radiologic tests are available 2

Important prognostic distinction: Patients with N1 disease have better prognosis than those with more extensive lymph node involvement or distant metastasis, and may benefit from aggressive treatment including cystectomy or chemoradiotherapy 2. Nodal cancer volume (diameter of largest metastasis and/or number of positive nodes) is closely linked to systemic progression risk 5.

M Classification (Distant Metastasis)

• M0: No distant metastasis 3
• M1a: Non-regional lymph node metastasis 6
• M1b: Bone metastasis - bone scintigraphy should be performed if bone metastases are suspected clinically, if tumor is poorly differentiated, or if PSA >10 mg/L 2
• M1c: Other distant metastasis with or without bone disease 6

Survival data for metastatic disease treated with primary androgen deprivation: 5-year overall survival is 76.0% for N1M0, 57.5% for M1a, 54.0% for M1b, and 40.0% for M1c, demonstrating worsening prognosis with stage progression 6.

Clinical vs. Pathological Staging

Critical distinction: Clinical staging (cTNM) is based on digital rectal examination, imaging, and biopsy before treatment, while pathological staging (pTNM) is based on surgical specimens after radical prostatectomy 1:

• Pathological staging is more predictive of prognosis than clinical staging and should be used when available 1
• Clinical staging understages tumors in up to 59% of cases and overstages in up to 5% when compared to pathological examination 3
• The modifier "c" before the stage refers to clinical staging; "p" refers to pathological staging 2

Staging Workup Requirements

Routine staging should include 2:

• Full blood count, alkaline phosphatase, creatinine, and serum total PSA
• Digital rectal examination
• Transrectal ultrasound to assess size, form, glandular structure, and possible capsular/seminal vesicle involvement
• Chest X-ray
• Bone scintigraphy if PSA >10 mg/L, tumor is poorly differentiated, or bone metastases are clinically suspected

Treatment Implications by Stage

Organ-confined disease (T1-T2, N0, M0): Suitable for curative local therapy including radical prostatectomy, external beam radiotherapy (≥66 Gy), or brachytherapy 2, 1

Locally advanced disease (T3-T4): Requires multimodal approaches - androgen suppression before, during, or after external beam radiotherapy significantly improves local control, reduces disease progression, and improves overall survival 2, 1

Node-positive disease (N1): May benefit from early hormonal therapy 1

Metastatic disease: Treatment is primarily hormonal with LHRH analogs accompanied by antiandrogen for 4 weeks 2

Integration with Other Prognostic Factors

TNM staging must be combined with Gleason score and PSA level for comprehensive risk assessment 1. The American College of Surgeons and National Comprehensive Cancer Network recommend using validated prognostic tools such as Partin tables that incorporate TNM staging to predict extraprostatic extension, seminal vesicle involvement, and lymph node involvement 1.