What is the recommended system for staging cancer?

Recommended Cancer Staging System

The TNM (Tumor-Node-Metastasis) staging system, developed and maintained jointly by the American Joint Committee on Cancer (AJCC) and the Union for International Cancer Control (UICC), is the universally recommended standard for cancer staging. 1

Primary Staging Framework

The TNM system quantifies the anatomical burden of cancer through three core components 1:

• T (Tumor): Size and local extent of the primary tumor
• N (Node): Extent of regional lymph node involvement
• M (Metastasis): Presence or absence of distant metastases

This classification was originally designed to measure anatomical disease extent and has become synonymous with prognosis due to consistent, robust associations between anatomical extent and patient outcomes. 1

Current Edition and Evolution

Use the AJCC 8th Edition (adopted January 2018) as the current standard, which represents a major advancement by integrating prognostic biomarkers with anatomic staging for select cancers. 2, 3, 4 The UICC and AJCC have collaborated since 1987 to ensure minimal differences between their classifications, striving for congruent definitions to enable consistent global use. 1

Integration of Biomarkers (8th Edition Innovation)

For certain cancers, particularly breast cancer, the 8th edition now incorporates 5, 2, 3:

• Hormone receptor status (estrogen and progesterone receptors)
• HER2 expression/amplification
• Tumor grade
• Multigene panel recurrence scores (when available)

These factors combine with anatomic TNM to create prognostic stage groups that provide superior individual prognostication compared to anatomic staging alone. 3, 4

Alternative Systems for Specific Contexts

While TNM remains the primary system, recognize these specialized alternatives 1:

• FIGO staging: Used for gynecologic malignancies (clinical, research, and surveillance)
• SEER Extent of Disease (EOD): Primarily for cancer surveillance community
• Essential TNM Classification: Simplified version for resource-limited settings (developed by UICC and IARC) 1

Site-Specific Considerations

Hepatocellular Carcinoma

TNM staging has limitations for HCC because both tumor burden and underlying liver function affect prognosis. 1 The modified UICC (mUICC) staging system is used in some regions (particularly Korea), though the AJCC/UICC TNM system remains the international standard. 1

Anal Cancer

Use the AJCC TNM system for anal canal cancer, but note that anal margin cancers use the skin cancer staging system due to similar biology. 1

Clinical vs. Pathologic Staging

Distinguish between two staging timepoints 6, 3:

• Clinical stage (cTNM): Established before treatment using physical examination, laboratory findings, and imaging studies
• Pathologic stage (pTNM): Determined after surgical resection with histologic examination of tissue; provides more accurate prognostication

Practical Implementation Algorithm

1. Obtain tissue diagnosis with histologic confirmation 1
2. Perform clinical staging using appropriate imaging (CT, MRI, PET-CT as indicated by cancer type) 1, 7
3. Determine biomarker status for cancers where integrated into staging (ER/PR/HER2 for breast cancer) 5, 2
4. Apply AJCC 8th Edition TNM criteria specific to the cancer site
5. Assign prognostic stage group incorporating both anatomic and biologic factors when applicable 3, 4
6. Use pathologic staging after definitive surgery to refine prognosis and guide adjuvant therapy 6

Critical Pitfalls to Avoid

Do not use outdated editions of the TNM system, as stage migration occurs with refinements in assessment methods and definitions. 1 The 8th edition (2018) represents the current standard, and using older editions will misclassify approximately 40% of patients in cancers with integrated biomarker staging. 3

Do not assume TNM staging alone determines treatment for all cancers—liver function is critical for HCC management decisions beyond stage. 1 Similarly, for rectal cancer, MRI-determined circumferential resection margin involvement drives neoadjuvant therapy decisions independent of T-stage alone. 7

Recognize that anatomic extent remains the foundation even as biomarkers are incorporated, because anatomic staging is more consistent over time and across geographic regions compared to evolving molecular factors. 1 The anatomic TNM should always be recorded separately to maintain continuity and enable use in settings where biomarker testing is unavailable. 3