Cancer of the lung is divided by cell type, location and progression. Doctors apply the system of lung cancer stages after a series of testing to determine tumor size, metastasis and involvement of the lymph nodes. The system is typically used to classify non-small cell cancers in the lungs and not the small cell type (SCLC.) Small cell cancers are suspected of metastasis when diagnosed and considered ‘extensive’ or ‘limited.’
Once doctors confirm the presence of lung cancer, testing begins. Tissue samples can be obtained through a needle biopsy inserted through the chest and into the lungs. A bronchoscopy procedure could be used to view the airways and retrieve samples as well. A third method called mediastinoscopy is used to view and collect samples from a lymph node in the chest.
Physicians analyze this data to develop a prognosis and course of treatment for the patient. Prognoses include survival without disease, general survival or declares a risk of recurring cancer.
TNM stands for tumor, lymph nodes and metastasis. The T represents the tumor’s size and starts at TX, a growth undetectable through imaging and scanning technology. Following TX are T0, (no tumor), Tis (in situ), and T1-T4. One through four relate to the size in centimeters. T1 is 3 cm or less, and is not invading the main bronchus. T2 is greater than 3 cm and is growing into the vital areas of the lungs.
T3 means a tumor of any dimension which has invaded the wall of the chest, the diaphragm, pleural cavity or the main stem bronchus. This designation puts the patient at risk for lung infections or other complications. A T4 tumor has grown into the heart or major vessels and arteries supplying it. It can also mean growth in the major airways, of any size.
Doctors use the TNM system to decide the stage the disease falls into. Stage 1a and 1b are early stages with the best prognosis. They refer to a T1 tumor with no lymph node involvement or metastasis. Stage 2a and 2b can indicate lymph nodes are involved, but generally no metastasis. As the stages progress in number, the prognosis is generally poorer.