Dr. Alberto De la Guerra

Appropriate staging of lung cancer is fundamental for determining the best treatment approach and defining prognosis. After ten years of labor the IASLC has modernized the lung cancer TNM staging system. Revisions to the TNM were determined by differences in the overall survival of 81,015 patients; after meticulous validation the proposals for changes were submitted to the AJCC and UICC, and accepted. The 7th edition of the “TNM Classification of Malignant Tumors” was launched recently, including the new lung cancer staging system. This article review and discusses the changes that appear in this new edition, which took effect for all new diagnosis of cancer on the first day of 2010

Following microscopic confirmation of lung cancer the anatomic extent of disease must be assessed to (1) separate patients who are candidates for surgical resection from those who are not, and will benefit from chemotherapy and/or radiotherapy, (2) determine prognosis. Staging also offers a common language to evaluate, compare and exchange information of treatment results and clinical research (1).

The basis for lung cancer staging is the tumor, node, and metastasis (TNM) classification developed and maintained collaboratively by the American Joint Committee on Cancer (AJCC) and the Union Internationale Contre le Cancer (UICC). The current system, the sixth edition of the TNM Classification of Malignant Tumors, was published in 2002. The last revision of the staging system for lung cancer was presented by Mountain in 1997 (2), which remained unaltered on the 2002 manual (3).

The staging system developed by Mountain was based on data collected from 5,319 patients with NSCLC, and was validated by Naruke in 2001 (4).

Proposals for a new Staging System

A staging system is not a static science; it requires periodic modifications to reflect new knowledge on cancer etiology, advances in diagnostic capabilities and staging procedures, along with improvements in therapy.

The current staging system has held up very well for 12 years, but has clear limitations. Several publications revealed problems in the T and N definitions, as well as variability of prognosis within the subsets of the stage groups (5-8). Revision of T, N, and M descriptors and the consequent stage groupings must be defined by the outcome measure of survival to improve the alignment of TNM stage with prognosis (9) to facilitate decisions about treatment options. Mountain’s revision was based on a relatively small population of patients who underwent surgical treatment in a single geographic area, and no validation was presented to justify the individual descriptors (10). Therefore, a revision was necessary (11-13).

In order to overcome the limitations of the present TNM classification, the International Association for the Study of Lung Cancer (IASLC) launched the Lung Cancer Staging Project in 1996 and, in 1998 created an International Staging Committee (ISC) of multidisciplinary members to conduct revisions (14).

Now, after a decade of work the IASLC has updated the lung cancer staging system. Changes to the sixth edition were proposed by the ISC based on an international collection and review of 100,869 patients from 46 sources of 20 countries. Data were drawn from lung cancer cases treated by all modalities between 1990 and 2000. After exclusion of ineligible cases, 81,015 patients (67,725 nsclc and 13,290 sclc) remained for investigation (15, 16). Data management and statistical analysis was carried out by the Cancer Research And Biostatistics “CRAB” (17).

Proposals for revision were submitted to the AJCC and UICC for consideration in the new edition of the staging manual and both accepted the recommendations. In the last months of 2009, the Seventh Edition of the TNM Classification of Malignant Tumorswas published, with a new lung cancer staging system. The new edition took effect on January 1, 2010 (18, 19).

Changes in lung cancer staging

"One enlarges science in two ways: by adding new facts
and by simplifying what already exists."
Claude Bernard (1813-1878).

The changes recommended by the IASLC for the future 7th edition of TNM classification for lung cancer were based on differences in survival (20), and the results of the data analysis were internally and externally validated (21). These changes include new T and M definitions and consequent new stage groupings, a new lymph node map, a novel definition on pleural invasion, as well as recommendations to apply the TNM system to broncho-pulmonary carcinoid tumors and SCLC.

Conclusions

So, what makes this latest review of the TNM system for lung cancer unique?

• The size of the database, the largest ever collected for any cancer type.
• For the first time, data was collected from different countries.
• The timeframe of 10 years allowed for 5 years follow-up.
• Cases included all treatment modalities.
• Pathologic and clinical staging where considered in survival analysis.
• The statistical analysis included meticulous internal and external validation.
• Changes to the TNM descriptors and stage groups were derived strictly from the outcome measure of overall survival.

The new TNM system is less intuitive and more complex than the 6th edition, and will be more difficult to learn. The oncology community needs to overcome the higher learning curve in order to offer patients the most appropriate treatment choices based on more accurate prognostic information.

Perfection is achieved, not when there is nothing more to add,
but when there is nothing left to take away.
—Antoine de Saint-Exupéry

by Doctors Lounge  Dr Alberto De la Guerra