Lung Cancer staging
October 17, 2011
What stage is my cancer, doc?
This is often the first question we get asked when meeting with a patient newly diagnosed with lung cancer. In this blog, I would like to briefly review the notion of lung cancer staging and its implications.
Staging allows us to define the extent of a cancer and determine its best available treatment. It also allows us to statistically estimate the prognosis of the cancer. Finally, adequate staging allows us to group patients with cancers of similar extent across different institutions or even countries and evaluate the efficacy of the treatment strategies and compare with new ones.
Staging can be clinical or pathological. Clinical staging is based on the information we obtain from X-rays and scans as well as from procedures where samples (biopsies) of different tissues are obtained in an effort determine what structures may be involved with the cancer. Pathological staging is only available when the cancer has been removed by surgery: i.e. when the pathologist has measured the size of the tumor, its extent and whether or not any lymph nodes were involved with cancer. One should be aware that pathological and clinical stagings don’t always concord 100%. Sometimes clinical staging under-evaluates how extensive the cancer may be, and at times it over-evaluates it, particularly when clinical staging is based only on X-ray information. This is particularly true with the evaluation of lymph nodes that drain the area where the cancer has come from. The role of your lung cancer surgeon in adequately gathering that information to develop the best treatment plan cannot be emphasized enough.
The system we use to define a stage is called the TNM system. T (0 to 4) refers to Tumor characteristics such as its size or whether it invades adjacent structures or not. For example a T1 tumor is less than 3 cm in size and does not invade any adjacent structure. A T3 tumor could be larger than 7 cm or may invade into the ribs next to the tumor. N (0 to 3) relates to whether the lymph nodes draining the lung are involved or not with cancer. Different node zones determine a different N number. M refers to whether or not the lung cancer has spread (metastasized) outside of the originating chest. Using the information obtained from the T, N and M characteristics we define groups as being a stage I, II, III or IV. Stages I to III can be further subdivided into As and Bs.
Using the staging information described above, we can make the best recommendation for treatment. As a rule, clinical stages I lung cancers are amenable for local means of treatment such as surgery or radiation therapy (“X-ray” treatments). Stages II and III lung cancers are usually considered for a combination of treatments of surgery, and/or radiation therapy and/or chemotherapy (drug treatments). The combination of these different treatments and the order with which we will apply them varies enormously and depends on different tumor and patient factors that are beyond the scope of this blog. Stage IV lung cancers for the most part are treated with chemotherapy alone though exceptions do exist.
In summary, we use various tests information to establish the stage of each cancer we treat. Staging allows us to define the extent of the cancer, its prognosis and best determine the treatment option(s) for each individual cancer patient we see.