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It depends on which cancer you are talking about and which staging system the doctor is using. Some types of cancer have more than one type of staging system. Most types of cancer have 4 stages. Often doctors write the stage down in roman numerals. So you may see stage 4 written down as stage IV. There is more about staging systems in the about cancer section of CancerHelp UK. The sections on each cancer type also have a page about staging and what the different stages mean.
Here is a brief summary of what the stages mean for most types of cancer
Stage 1 usually means a cancer is relatively small and contained within the organ it started in
Stage 2 usually means the cancer has not started to spread into surrounding tissue, but the tumour is larger than in stage 1. Sometimes stage 2 means that cancer cells have spread into lymph nodes close to the tumour
Stage 3 usually means the cancer is larger. It may have started to spread into surrounding tissues and there are cancer cells in the lymph nodes in the area
Stage 4 means the cancer has spread from where it started to another body organ - this is also called secondary or metastatic cancer
http://www.cancerhelp.org.uk/about-cancer/cancer-questions/how-many-stages-of-cancer-are-there cited 27/09/2010
Following a positive identification of cancer, doctors will try to establish the stage of the cancer. Cancers are ranked into stages depending on the specific characteristics that they possess; stages correspond with severity. Determining the stage of a given cancer helps doctors to make treatment recommendations, to form a likely outcome scenario for what will happen to the patient (prognosis), and to communicate effectively with other doctors.
There are multiple staging scales in use. One of the most common ranks cancers into five progressively more severe stages: 0, I, II, III, and IV. Stage 0 cancer is cancer that is just beginning, involving just a few cells. Stages I, II, III, and IV represent progressively more advanced cancers, characterized by larger tumor sizes, more tumors, the aggressiveness with which the cancer grows and spreads, and the extent to which the cancer has spread to infect adjacent tissues and body organs. Another popular staging system is known as the TNM system, a three dimensional rating of cancer extensiveness. Using the TNM system, doctors rate the cancers they find on each of three scales, where T stands for tumor size, N stands for lymph node involvement, and M stands for metastasis (the degree to which cancer has spread beyond its original locations). Larger scores on each of the three scales indicate more advanced cancer. For example, a large tumor that has not spread to other body parts might be rated T3, N0, M0, while a smaller but more aggressive cancer might be rated T2, N2, M1 suggesting a medium sized tumor that has spread to local lymph nodes and has just gotten started in a new organ location.
Still another staging system, called summary staging, is in use by the National Cancer Institute for its SEER program. Summary stages include: "In situ" or early cancer (stage 0 cancer), "localized" cancer which has not yet begun to spread, "regional" cancer which has spread to local lymph nodes but not yet to distant organs, "distant" cancer which has spread to distant organs, and finally, "unknown" cancer to describe anything not fitting elsewhere.
The following stages are used to describe cancer of the lip and oral cavity:
The cancer is less than 2 centimeters in size (about 1 inch), and has not spread to lymph nodes in the area (lymph nodes are small almond shaped structures that are found throughout the body which produce and store infection-fighting cells).
The cancer is more than 2 centimeters in size, but less than 4 centimeters (less than 2 inches), and has not spread to lymph nodes in the area.
Either of the following may be true: The cancer is more than 4 centimeters in size. The cancer is any size but has spread to only one lymph node on the same side of the neck as the cancer. The lymph node that contains cancer measures no more than 3 centimeters (just over one inch).
Any of the following may be true: The cancer has spread to tissues around the lip and oral cavity. The lymph nodes in the area may or may not contain cancer. The cancer is any size and has spread to more than one lymph node on the same side of the neck as the cancer, to lymph nodes on one or both sides of the neck, or to any lymph node that measures more than 6 centimeters (over 2 inches). The cancer has spread to other parts of the body.
Several different systems are used for ranking cancers by stage in the process of developing a treatment program. Staging cancers is important, because it allows a doctor to assess a cancer and use standardized terminology to describe it, so that the medical team can work together to develop the best course of treatment. Stages are ranked in order of severity, with slow or non-aggressive cancers at the bottom of the scale, and fast-moving, severe cancers at the top.
One very common system for staging cancers runs from zero to four, with a stage zero cancer being the least severe, while four is the most aggressive. An alternate numbered staging system is depicted in Roman numerals, with the option of I, II, III, and IV. Some physicians break the Roman numeral staging system down even further, with classifications like IIa and IIb to describe cancers which fall slightly between the stages.
Some doctors use the TNM system to stage cancers, which ranks a cancer with three separate parameters: tumor size, lymph node involvement, and metastasis. For example, someone could have a T3, N0, M1 cancer, meaning that the tumor was medium-sized, no lymph nodes are involved, and the cancer has begun to metastasize slightly.
Other oncologists refer to in situ, localized, regional, and distant cancers when they talk about cancer staging. In situ cancers are cancers which only involve a few cells, meaning that they are caught early or they develop slowly. Localized cancers affect a larger area, while regional cancers are cancers which have begun to spread to neighboring organs and lymph nodes. In a distant cancer, the cancer has spread to remove areas of the body, reflecting a widespread metastasis. This system is essentially interchangeable with the Roman numeral system of staging.
All types of cancer can be ranked under a staging system, including breast, colon, lung, and cervical cancers. Lower stages usually require less aggressive treatment, because the cancer is confined to a small area, and it may be able to be excised and eliminated. Higher stages of cancer require more serious treatment, and in some cases, a high stage cancer may be deemed untreatable as a result of its persistent and wide spread.
Doctors sometimes disagree over the staging of a particular cancer, and seeking a second opinion can sometimes generate conflicting information. If doctors do give different answers, it is a good idea to ask about why they disagree on their staging assessment, and how their treatment approaches might differ.
Cancer is a disease in which cells grow out of control and invade,
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Cancer staging systems describe how far cancer has spread anatomically and attempt to put patients with similar prognosis and treatment in the same staging group. Since prognosis and treatment depend quite a bit on the stage, you can see how important it is to know what stage you have! At the same time other factors, including your general health, your own preference, and the results of biochemical tests on your cancer cells will contribute to determining the prognosis and treatment. So while the stage is important it is not everything.
The concept of stage is applicable to almost all cancers except for most forms of leukemia. Since leukemias involve all of the blood, they are not anatomically localized like other cancers, so the concept of staging doesn't make as much sense for them. A few forms of leukemia do have staging systems which reflect various measures of how advanced the disease is. For most solid tumors, there are two related cancer staging systems, the Overall Stage Grouping, and the TNM system.
Overall Stage Groupings (Roman Numeral Staging)
In this system, cases are grouped into four stages denoted by Roman numerals I through IV, or are classified as "recurrent." In general, stage I cancers are small localized cancers that are usually curable, while stage IV usually represents inoperable or metastatic cancer. Stage II and III cancers are usually locally advanced and/or with involvement of local lymph nodes. Actually, these stages are defined precisely, but the definition is different for each kind of cancer. In addition, it is important to realize that the prognosis for a given stage also depends on what kind of cancer it is, so that a stage II non small cell lung cancer has a different prognosis from a stage II cervical cancer.
Unfortunately, it is common for cancer to return months or years after the primary tumor has been removed because cancer cells had already broken away and lodged in distant locations by the time the primary tumor was discovered, but had not formed tumors which were large enough to detect at that time. Sometimes a tiny bit of the primary tumor was left behind in the initial surgery and this later grows into a macroscopic tumor. Cancer that recurs after all visible tumor has been eradicated, is called recurrent disease. Disease that recurs in the area of the primary tumor is locally recurrent, and disease that recurs as metastases is referred to as a distant recurrence. Distant recurrence is usually treated similarly to stage IV disease (sometimes the terms are used interchangeably) and anyone in this situation should investigate options for both stage IV and recurrent disease. The significance of a Local recurrence may be quite different than distant recurrence, depending on the type of cancer.
For solid tumors, stages I-IV are actually defined in terms of a more detailed staging system called the "TNM" system.
In the TNM system, TNM stands for Tumor, Nodes, and Metastases. Each of these is categorized separately and classified with a number to give the total stage. Thus a T1N1M0 cancer means the patient has a T1 tumor, N1 lymph node involvement, and no distant metastases. Of course the definitions of T, N and M are specific to each cancer, but it is possible to give a general idea of what they mean.
T Classifies the extent of the primary tumor, and is normally given as T0 through T4. T0 represents a tumor that has not even started to invade the local tissues. This is called "In Situ". T4 on the other hand represents a large primary tumor that has probably invaded other organs by direct extension, and which is usually inoperable.
N: Lymph Nodes
N classifies the amount of regional lymph node involvement. It is important to understand that only the lymph nodes draining the area of the primary tumor are considered in this classification. Involvement of distant lymph nodes is considered to be metastatic disease. The definition of just which lymph nodes are regional depends on the type of cancer. N0 means no lymph node involvement while N4 means extensive involvement. In general more extensive involvement means some combination of more nodes involved, greater enlargement of the involved nodes, and more distant (But still regional) node involvement.
M is either M0 if there are no metastases or M1 if there are metastases.
As with the other system, the exact definitions for T and N are different for each different kind of cancer.
As you can see, the TNM system is more precise than the I through IV system and certainly has a lot more categories. The two systems are actually related. The I through IV groupings are actually defined using the TNM system. For example, stage II non-small cell lung cancer means a T1 or T2 primary tumor with N1 lymph node involvement, and no metastases (M0).
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 staging 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.
How To Find The Staging System For Your Cancer
In order to understand the entire staging system for your kind of cancer, you can consult a book [See Book Recommendations], but you can get also basic staging information on the web from The National Cancer Institute. To find it, go to their Cancer information by Type section, find the page for your type of cancer, and then click on the treatment statement for your type of cancer. There is both a patient and professional statement - the patient statement will have a simplified version and it's good to look at this before tackling the more detailed and technical professional version.
Perspective is Important!
It is important to know that while stages are an important guide to treatment and prognosis, they are certainly not the whole story. There can be many individual situations within these stage groupings. For instance, if a patient with kidney cancer has only one metastasis and it can be removed surgically, and it's been several years since he had his kidney out, the prognosis is much better than if he had many metastases which appeared just after surgery to remove the kidney. Sometimes the treatment depends on just where metastases are located. There are, for instance, specialized methods for treating bone metastases and brain metastases. If a new treatment becomes available, some sub-group of patients within a certain stage may suddenly have a much better prognosis. If you find such a treatment, then you have a much better prognosis! Finally, it's important to keep in mind that there is considerable variation in outcome for every type and stage of cancer. A prognosis associated with a cancer stage is only a general guide, not an infallible prediction, a sentence, or a guarantee. I highly recommend Stephen Jay Gould's The Median Isn't the Message to get a healthy perspective on prognostic statistics.