HONG KONG RESPIRATORY MEDICINE

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2010 Jan - Revised Lung Cancer Staging (2009) - Rationale and Changes

Dr. James Ho, Department of Medicine, The University of Hong Kong. Jan 2010
The new TNM staging system (7th edition) for lung cancer has recently been adopted by the International Association for the Study of Lung Cancer (IASLC), International Union Against Cancer (UICC) and American Joint Committee on Cancer (AJCC) earlier in 2009. This was largely based on the survival data of more than 100,000 patients in a study conducted under the initiative of the IASLC since 1998.1 With the new TNM descriptors, the revised overall staging can provide better prognostic stratification. The following highlights some of the major principles of the new staging system (Table 1):
 
6th edition T/M descriptor
Revised T/M descriptor
N0
N1
N2
N3
T1 (≤2cm)
T1a
IA
IIA
IIIA
IIIB
T1 (>2-3cm)
T1b
IA
IIA
IIIA
IIIB
T2 (>3-5 cm)
T2a
IB
IIA
IIIA
IIIB
T2 (>5-7cm)
T2b
IIA
IIB
IIIA
IIIB
T2 (>7cm)
T3
IIB
IIIA
IIIA
IIIB
T3 invasion
T3
IIB
IIIA
IIIA
IIIB
T4 (same lobe nodules)
T3
IIB
IIIA
IIIA
IIIB
T4 (extension)
T4
IIIA
IIIA
IIIB
IIIB
M1 (ipsilateral lung)
T4
IIIA
IIIA
IIIB
IIIB
T4 (pleural effusion)
M1a
IV
IV
IV
IV
M1 (contralateral lung)
M1a
IV
IV
IV
IV
M1 (distant)
M1b
IV
IV
IV
IV
Table 1. Overall stage in bold indicates a change from 6th edition of TNM staging. (Adapted from reference)

1. Primary tumour size (T): the previous staging defined T1 and T2 by the cut-off at 3 cm of tumour size, while a huge tumour (e.g. 10 cm) will still be described as T2 if there is no involvement beyond the visceral pleura and > 2 cm from the carina. The new staging provides more precise sub-categorization of T descriptors (T1a, T1b, T2a, T2b) by additional cut-off tumour sizes at 2, 3, 5, and 7 cm. Tumours larger than 7 cm is now described as T3 rather than T2. This would allow better correlation between tumour size and prognosis, i.e. larger tumours are associated with a worse prognosis and more advanced overall staging.
2. Satellite nodules in the same lobe: separate lung nodules within the same lobe as the primary tumour was previously described as T4. Under the new staging system, such satellite nodules will be defined as T3. This is in keeping with consideration of lobectomy for such cases in the absence of advanced nodal or distant metastases, despite having an overall stage IIIB in the old staging system.
3. Malignant pleural or pericardial effusion: the so-called “wet IIIB” in the old staging describes malignant involvement of pleural or pericardial effusion. However, the clinical management and prognosis of such cases have been considered exactly the same as those with distant metastases, thus appropriately classified as M1a in the new staging system.
4. Metastatic lung nodules beyond the same lobe as the primary tumour (M): all metastatic lung nodules apart from those within the same lobe as the primary tumour have been considered distant metastases and described as M1 in the previous staging. Under the new staging system, such metastatic lung nodules ipsilateral to the primary tumour will be described as T4, while those contralateral lung nodules as M1a.
5. Distant metastases apart from lung: all distant metastases except in lungs will be described as M1b.
6. Nodal staging: N descriptors (N0-3) are largely similar but better defined anatomically under the new staging system.
Tumour staging has been the cornerstone in oncology, which allows accurate prognostication and standardization of treatment strategies. In the era of multi-disciplinary team approach, all medical professionals (pulmonologists, oncologists, thoracic surgeons, pathologists, radiologists) involved in the clinical management of lung cancer should become familiar with the updated staging system.


Reference
Goldstraw P, Crowley J, Chansky K, Giroux DJ, Groome PA, Rami-Porta R, Postmus PE, Rusch V, Sobin L; International Association for the Study of Lung Cancer International Staging Committee; Participating Institutions. The IASLC Lung Cancer Staging Project: proposals for the revision of the TNM stage groupings in the forthcoming (seventh) edition of the TNM Classification of malignant tumours. J Thorac Oncol 2007;2(8):706-14.