What is the New Lung Cancer Staging System?

In July 2009 a new lung cancer staging system was revealed: The 7^th edition of the Tumor/LymphNode/Metastasis (TNM) classification. The 7^th edition TNM classification is a result of the International Staging Committee (ISC) created by the International Association for the Study of Lung Cancer (IASLC), resulting in the IASLC Lung Cancer Retrospective Staging Project.¹

The ISC compiled clinical data on over 100,000 patients diagnosed with NSCLC and SCLC between 1990 and 2000, making the patient population examined 20 times the size of the 1997 analysis. All components of the staging system were considered for upgrading, with the majority of changes occurring in the T and M components.¹

The 6^th staging edition divided tumors into two size groups: T1 < 3cm in diameter, and T2 ≥ 3cm in diameter. However, most thoracic surgeons and medical oncologists can anecdotally attest that the biologic behavior of node negative tumors that are 6-7cm, behave differently then 3cm node negative tumors, despite both being in the same broad T2 grouping. The ISC confirmed this assumption. Results suggested that new size groupings should be created of 2, 3, 5 and 7cm. 5 year survival rates for the pathologic groupings with negative nodes and no metastasis were 77% for T1 ≤ 2cm, 71% for T1 > 2cm and ≤ 3cm, 58% for T2 > 3cm and ≤ 5cm, 49% > 5cm and ≤ 7cm and 35% for T2 > 7cm. Subsequently, the ISC recommended subclassifying T1 into T1a (≤ 2cm) and T1b (>2cm and ≤3cm) and subclassifying T2 into T2a (> 3cm but ≤ 5cm or tumor with any other T2 descriptors, but ≤ 5cm) and T2b (> 5cm but ≤ 7cm), and reclassify T2 tumors > 7cm to T3.²

No formal changes were recommended for nodal staging. Malignant pleural effusion was reclassified to M1a. The ISC found that extrathoracic metastasis had poorer prognosis than intrathoracic metastasis. M1 was therefore sub-classified to M1a for additional tumors in the contralateral lung, malignant pleural and pericardial effusions, and nodular pleural dissemination, and M1b for extrathoracic metastasis.^3,4

The new stage groupings are as follows: T2b tumors ((> 5cm but ≤ 7cm) that are N0M0 are upstaged from IB to IIA; T2a tumors (≤ 5cm) that are N1M0 are down staged from IIB to IIA, and T4 tumors that are N0/1 are down staged to IIIA. Restaging the patient population in the study based on the proposed 7^th TNM edition, found a pathologic 5 year survival rate 73% for IA, 58% for IB, 46% for IIA, 36% for IIB, 24% for IIIA, 9% for IIIB and 13% for IV.⁵

The 7^th edition TNM staging system for NSCLC is an exciting accomplishment, and will help the clinician to better understand the outcomes of lung cancer and offers an exciting advance to our specialty.

1. Rami-Porta R, Crowley JJ, Goldstraw P. The revised TNM staging system for lung cancer. Ann Thorac Cardiovasc Surg. 2009 Feb;15(1):4-9.
2. Rami-Porta R, Ball D, Crowley J, et al. The IASLC Lung Cancer Staging Project: proposals for the revision of the T descriptors in the forthcoming (seventh) edition of the TNM classification for lung cancer. J Thorac Oncol. 2007 Jul;2(7):593-602.
3. Rusch VW, Crowley J, Giroux DJ, et al. The IASLC Lung Cancer Staging Project: proposals for the revision of the N descriptors in the forthcoming seventh edition of the TNM classification for lung cancer. J Thorac Oncol. 2007 Jul;2(7):603-12.
4. Postmus PE, Brambilla E, Chansky K, et al. The IASLC Lung Cancer Staging Project: proposals for revision of the M descriptors in the forthcoming (seventh) edition of the TNM classification of lung cancer. J Thorac Oncol. 2007 Aug;2(8):686-93.
5. nbsp; Goldstraw P, Crowley J, Chansky K, et al. 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 Aug;2(8):706-14. Erratum in: J Thorac Oncol. 2007 Oct;2(10):985.
6. Rusch VW, Asamura H, Watanabe H, et al. The IASLC lung cancer staging project: a proposal for a new international lymph node map in the forthcoming seventh edition of the TNM classification for lung cancer. J Thorac Oncol. 2009 May;4(5):568-77.