Stage is determined by three factors, T, N and M.

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This page was last revised on February 10, 2004.

T represents the size of the tumor and whether it has invaded into surrounding structures such as the ribs or the heart.

N represents the lymph nodes involved by metastasis from the lung tumor.

M describes whether spread to other organs has occured.

A tumor has a characteristic life cycle in most cases. As mentioned earlier, it goes through many years of increasing mutations before it becomes a cancer. In it's earliest stages, it has the appearance of a cancer under the microscope, but has not yet begun to invade surrounding tissues. This stage is called "in situ" carcinoma. This stage is rarely detected clinically.

Once the tumor begins to invade it is a true cancer. It then will grow larger in it's local surroundings. It is in stage I. During this stage, it seldom causes symptoms. If the tumor is discovered by screening, or fortuitously in stage I, it can be cured by surgical resection.

As the tumor grows, there is an increasing tendency for it to invade lymphatic channels and blood vessels. When the tumor cells move through the lymphatic channels and begin to grow in lymph nodes in the hilum of the lung (N=1), the tumor has reached stage II. In this stage, the tumor can still be cured by surgical resection in some cases, but the rate of failure is significantly higher than in Stage I. The % of lung cancers with hilar nodal metastases correllates very closely with the size of the primary tumor. Lung cancers of one centimeter in diameter have a very low % <10% incidence. Tumors of three centimeters diameter have approximately a 30% incidence of hilar nodal metastasis.

Because tumors that have hilar metastases have a lower cure rate after surgery, it is my practice to recommend adjuvant radiation therapy after surgical resection. Although this has not been definitively proven to increase long term survival, it has been proven to reduce the chances of recurrent cancer in the chest.

When the primary tumor has complicating factors (T=3) or the mediastinal lymph nodes on the same side of the chest are involved (N=2), then the tumor is in Stage IIIA. The chance of cure in these patients is further reduced and surgery is possible in only carefully selected cases.

Stage IIIB has further advanced local and lymph nodal growth, and is not currently curable by surgery alone.

When metastasis to distant organs, most commonly brain and bone occurs (M=1) then the patient is in Stage IV. Only an occasional patient with a single metastasis to the brain can be cured by surgical removal of the lung and brain cancers with separate operations. This past year there were some new changes in the international staging system for staging of lung cancer reflecting new knowledge relating to curability of lung cancer. Stage I now consists of two groups, Stage IA representing patients with T1N0M0 status and Stage IB representing patients with T2N0M0 status. Stage II is similarly split into two groups, Stage IIA representing patients with T1N1M0 and Stage IIB representing patientw with T2N1M0. In addition, patients with T3N0M0 who were formerly Stage IIIA have now been included into Stage IIB. Patients with T3N1M0 remain in Stage IIIA which remains otherwise unchanged as does Stage IV. Clifton Mountain. Special Report Revisions in the International System for Staging Lung Cancer. Chest 1997;111:1710-17. (See also pp 1718-23 and 1486 in the same issue.)

More on stage CTSNET has an entire textbook of lung cancer screening with examples available on the web.

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