Staging System Variations and Changes

There is no law of nature that all cancers are best classified into just four prognostic groups. For many cancers four prognostic groups is not enough, so the overall staging is further divided with classifications like IIa, and IIIb. (A few cancers have fewer than four stage groupings.) You may find it natural to assume that the differences in prognosis between sub-groups, like IIIa and IIIb, is smaller than between major divisions like II and III, but this is not necessarily the case. For instance in non-small cell lung cancer, the difference between stage IIIa and stage IIIb is very important. People with stage IIIa cancer have a chance of being cured with treatment which includes surgery, whereas surgery generally does not help people with stage IIIb who have a substantially worse prognosis. Again, you must find the specific stating and prognostic information for your cancer to know what the staging means in terms of prognosis. For leukemias and other cancers which don't form solid tumors, the staging is again different. Because there is not a localized primary tumor with distinct metastasis to lymph nodes and other organs, the TNM system simply doesn't apply. Often there are defined stages I through IV but if so it will depend on various factors such as the blood count, extent of bone marrow involvement or the presence or absence of symptoms. Although the trend is towards standard terminology, some types of cancers use staging systems with different nomenclatures. For example, prostate and colon cancer are sometimes staged as A through D rather than I through IV. In these cases, unfortunately there is more than one staging system in use at the same time! Obviously you need to be aware of which staging system is being used in a particular paper or reference, and which was used in your case. Usually, the staging used will be referenced according to the originator of the paper - e.g. the Duke staging system for colon cancer. Often you can figure out what your stage was in the "other" system with specific information about the extent of your cancer from your pathology and operative reports. As if this weren't enough, new information and improvements in treatment changes the prognosis or treatment of various subgroups, and as a result, the staging system for individual cancers must be revised from time to time. If you are relying on recent information, as you should be, then you will usually be looking at research data based on the latest staging, but be alert for the possibility that the staging just recently changed for your cancer so that some relatively recent papers use the older system.