What is the lung cancer staging system for a patient with non-small cell lung cancer (NSCLC) and completely resected N1 disease, based on the Tumor (T), Node (N), Metastasis (M) classification?

Lung Cancer TNM Staging System

The current staging system for non-small cell lung cancer (NSCLC) uses the 7th edition TNM classification, which defines stage groupings based on tumor size (T), lymph node involvement (N), and distant metastases (M). 1

TNM Classification Components

T (Tumor) Descriptors - 7th Edition

The 7th edition introduced refined size-based T classifications 1:

• T1a: ≤2 cm 1
• T1b: >2 to 3 cm 1
• T2a: >3 to 5 cm 1
• T2b: >5 to 7 cm 1
• T3: >7 cm or tumors with satellite lesions in the same lobe 1

N (Node) Descriptors

The nodal classification remains consistent across editions 2, 3, 4:

• N0: No regional lymph node metastasis 2, 3, 4
• N1: Metastasis to ipsilateral peribronchial and/or ipsilateral hilar lymph nodes 2, 3, 4
• N2: Metastasis to ipsilateral mediastinal and/or subcarinal lymph nodes 2, 3, 4
• N3: Metastasis to contralateral mediastinal, contralateral hilar, ipsilateral or contralateral scalene, or supraclavicular lymph nodes 2, 3, 4

M (Metastasis) Descriptors

• M0: No distant metastasis 2
• M1: Distant metastasis present 2, 5

Stage Groupings for Early-Stage NSCLC

Stage I

• Stage IA: T1a-b N0 M0 1
• Stage IB: T2a N0 M0 1

Stage II

• Stage IIA: T2b N0 M0 OR T1a-b N1 M0 OR T2a N1 M0 1
• Stage IIB: T2b N1 M0 OR T3 N0 M0 1

Stage III

• Stage IIIA: T3 N1 M0 OR T1-3 N2 M0 1
• Stage IIIB: T4 N0-2 M0 OR T1-4 N3 M0 1

Stage IV

• Stage IV: Any T, Any N, M1 1, 5

Clinical Application for N1 Disease

For patients with completely resected pathologic stage IIA,B (N1) NSCLC, the specific stage depends on the T descriptor combined with N1 involvement 1:

• T1a-b N1 M0 = Stage IIA 1
• T2a N1 M0 = Stage IIA 1
• T2b N1 M0 = Stage IIB 1

Prognostic Significance of N Descriptors

The N0 through N3 descriptors consistently separate prognostically distinct groups 3, 4:

• N0: 5-year survival 75% (pathologic) 3
• N1: 5-year survival 49% (pathologic) 3
• N2: 5-year survival 36% (pathologic) 3
• N3: 5-year survival 20% (pathologic) 3

Important Staging Considerations

Clinical vs. Pathological Staging

• Clinical staging (cTNM) is established before treatment using imaging, physical examination, and biopsy 2
• Pathological staging (pTNM) is determined after surgical resection with histologic examination and provides more accurate prognostic information 2, 3

Common Pitfalls to Avoid

• Inadequate lymph node sampling: Ensure examination of >12 lymph nodes for accurate pathologic staging 2
• Imaging limitations: CT and PET may not reliably detect microscopic nodal metastases in normal-sized nodes 2
• Unexpected nodal metastasis: 19.4% of clinical stage I patients have pathologic nodal involvement, particularly with larger tumors and solid consistency 6

Treatment Implications Based on Staging

For completely resected pathologic stage IIA,B (N1) NSCLC with good performance status, postoperative platinum-based chemotherapy is recommended (Grade 1A) 1. This represents a critical treatment decision point where accurate pathologic staging directly impacts survival outcomes through appropriate adjuvant therapy selection.