Malignant non-small cell epithelial tumors of the lung are classified by the World Health Organization (WHO)/International Association for the Study of Lung Cancer (IASLC). There are three main subtypes of non-small cell lung cancer (NSCLC), including the following:
Squamous cell carcinoma (25% of lung cancers).
Adenocarcinoma (40% of lung cancers).
Large cell carcinoma (10% of lung cancers).
There are numerous additional subtypes of decreasing frequency.
American Joint Committee on Cancer (AJCC) Tumor, Node, and Metastasis (TNM).
Veterans Administration Lung Study Group (VALG).
International Association for the Study of Lung Cancer (IASLC).
No universally accepted definition of this term is available. Limited-stage disease (LD) SCLC is confined to the hemithorax of origin, the mediastinum, or the supraclavicular nodes, which can be encompassed within a tolerable radiation therapy port.
Patients with pleural effusion, massive pulmonary tumor, and contralateral supraclavicular nodes have been both included within and excluded from LD by various groups.
Extensive-stage disease (ED) SCLC has spread beyond the supraclavicular areas and is too widespread to be included within the definition of LD. Patients with distant metastases (M1) are always considered to have ED.[3,4]
IASLC-AJCC TNM Staging System
The AJCC TNM defines LD as any T, except for T3-4, due to multiple lung nodals that do not fit in a tolerable radiation field, any N, and M0. This corresponds to TNM stages I to IIIB. Extensive disease is TNM stage IV with distant metastases (M1) including malignant pleural effusions.[3,4]
The IASLC conducted an analysis of clinical TNM staging for SCLC using the sixth edition of the AJCC TNM staging system for lung cancer. Survivals for patients with clinical stages I and II disease are significantly different from those for patients with stage III disease with N2 or N3 involvement. Patients with pleural effusion have an intermediate prognosis between LD and ED with hematogenous metastases and will be classified as having M1 disease (or ED). Application of the TNM system will not change how patients are managed; however, the analysis suggests that, in the context of clinical trials in LD, accurate TNM staging and stratification may be important.
Staging procedures for SCLC are important in distinguishing patients with disease limited to their thorax from those with distant metastases. At the time of initial diagnosis, approximately two-thirds of patients with SCLC have clinical evidence of metastases; most of the remaining patients have clinical evidence of extensive nodal involvement in the hilar, mediastinal, and sometimes supraclavicular regions.
Determining the stage of cancer allows an assessment of prognosis and a determination of treatment, particularly when chest radiation therapy or surgical excision is added to chemotherapy for patients with LD. If ED is confirmed, further evaluation should be individualized according to the signs and symptoms unique to the individual patient. Standard staging procedures include the following: