LUNG CANCER STAGING
In 2010, the
International Union Against Cancer (UICC) and the American Joint Committee on
Cancer (AJCC) published the revised seventh edition of the TNM (tumor, node,
metastasis) staging system. This seventh edition was developed on the basis of
the International Association for the Study of Lung Cancer (IASLC) and proposed
changes to the classification from analysis of more than 67,000 cases of
non–small cell lung cancer from around the world. This was the largest data set
ever analyzed for the purpose of developing and validating a new staging
system. The proposed new TNM staging system has also been validated for small
cell carcinoma and bronchial carcinoid tumors. The primary determinant of each
T, N, and M descriptor, as well as the overall stage grouping, was based on
survival. Detailed algorithms were used to identify unique stages in the simplest
way with the least overlap. Stages were internally and externally validated for
out-comes across the various databases and geographic regions from which the
data were gathered.
There were a number of substantial changes made to the former (sixth) staging system:
1. T1 tumors were divided
into T1a (tumors ≤2 cm in greatest diameter) and T1b (tumors >2 cm but ≤3 cm in greatest dimension).
2. T2 tumors were divided
into T2a (tumors >3 cm but ≤5 cm in greatest diameter) and T2b (tumors >5 cm but ≤7 cm in
greatest dimension).
3. Tumors more than 7 cm
in greatest dimension are classified as T3.
4. Tumors with additional
nodule(s) in the same lobe are classified as T3.
5. Tumors with additional
nodule(s) in another ipsilateral lobe are classified as T4.
6. Pleural dissemination
(malignant pleural or pericardial effusions, pleural nodules) is classified as
M1a.
7. The lymph node
classification remained the same, with N1 as intrapulmonary or ipsilateral
hilar, N2 as ipsilateral mediastinal or subcarinal, and N3 as contralateral
mediastinal or supraclavicular.
8. Incorporated proposed
changes to T and M (affects T2, T3, T4, and M1 categories).
9. Reclassify T2aN1
tumors (≤5 cm) as stage IIA (from IIB).
10. Reclassify T2bN0
tumors (>5 cm to 7 cm)
as stage IIA (from IB).
11. Reclassify T3 (tumor >7 cm) N0M0 as stage
IIB (from IB).
12. Reclassify T4N0 and
T4N1 as stage IIIA (from IIIB).
13. Reclassify pleural
dissemination (malignant pleural or pericardial effusions, pleural nodules)
from T4 to M1a.
14. Subclassify M1 by
additional nodules in contralateral lung as M1a.
15. Subclassify M1 by
distant metastases (outside the lung/pleura) as M1b.
Because of the addition of new T and M descriptors,
the staging definitions have clearly become more complex. However, the new
system now provides a more validated system for defining prognosis. In addition,
the system also allows common terminology to be used across the world to
describe similar patients, which is critical for accurate communication across the medical community and the conduct of
worldwide clinical trials. A future goal is the further refinement of the
classification system to include the biologic behavior of lung tumors, not just
anatomic location, which should promote understanding of tumor biology and
provide guidance toward more specific therapies.
