What Are The Stages Of Cancer?
Cancer is a disease where the cells in an individual's body begin to grow excessively fast and out of control. This process causes damage and crowding out of healthy cells and robs the healthy cells of crucial nutrients required to keep them alive. Cancer occurs when a cell experiences damage that changes a part of the cellular DNA responsible for cell growth, multiplication, differentiation, and apoptosis. Once an individual is diagnosed with cancer, their oncologist must run further tests to determine how extensive and severe the cancer is. The stage of cancer will play a significant role in determining what methods are used for treatment and the patient's long-term prognosis. The clinical-stage of a patient's cancer is the stage of their cancer before undergoing any treatment and the pathologic stage is the stage of following treatment.
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Why Cancers Are Staged
Cancer is staged for several reasons important to the process of treatment and management of the disease. Cancer staging helps determine the prognosis of a patient's cancer or expectations of the disease pattern and outcome. The most common staging system used for cancer is referred to as the TNM staging system. The T component is a stage that refers to the size, presence, and extension of the primary tumor. The N component of the staging system refers to the level of nearby or distant lymph node cancer infiltration. The M component of the staging system describes the presence of cancer metastasis to distant areas of the patient's body. In each TNM component, the different types of cancer are further broken down into stage groups ranging from stage 0 to stage 4 based on how far the cancer has spread. Prognosis statistics for each stage group are determined by current data from thousands of patients diagnosed with the particular type and stage of cancer.
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Stage 1
Stage 1 cancer refers to a malignancy that is small in size and has not spread beyond its original location to the lymph nodes or other distant areas in the body. Each different type of cancer has criteria for what stage 1 is defined as with reference to the TNM system. The N and M groupings almost always remain at N0 and M0 in stage 1 cancer, indicating cancer has not spread into neighboring lymph nodes or distant tissues. In the staging criteria for most cancer types, the T grouping in stage 1 cancer is T1. A T1 grouping usually includes a maximum diameter measurement for the solid tumor. For example, a tumor in the breast that measures up to two centimeters across has a T1 grouping. Some types of cancer include a grouping of T2 with an increased tumor diameter measurement threshold that picks up where the T1 grouping left off. The majority of stage 1 cancers have a TNM grouping of T1-N0-M0 or T2-N0-M0.
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Stage 2
Stage 2 cancer refers to a solid malignancy that has grown to a larger size than what a stage 1 cancer is, but has not begun to spread into nearby tissues besides three or less neighboring lymph nodes. The criteria for stage 2 also varies between different types of cancer when it comes to exact tumor measurements and the number of infiltrated lymph nodes. Stage 2 cancer typically has a T grouping of T1, T2, and in some types T3. A T3 grouping means the tumor is larger in diameter than the range defined for a T2 grouping, with the T3 measurement picking up where the T2 measurement left off. Stage 2 cancer usually only includes N groupings of N0 and N1. An N1 grouping refers to cancer that has spread into neighboring lymph nodes around the tumor but only up to a specified number of them. The M grouping remains at M0 in the majority of cancer types considered to be stage 2. Most stage 2 types of cancer encompass a TNM grouping of T1-N1-M0, a grouping of T2-N0-M0, a grouping of T2-N1-M0, and a grouping of T3-N0-M0.
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Stage 3
Stage 3 cancer refers to a solid malignant tumor that has grown into nearby tissues at a larger size than in stage 2 cancer and has spread into a higher number of neighboring lymph nodes. The exact number of affected lymph nodes and the exact tumor measurements in the criteria for stage 3 can vary from one type of cancer to the next. Stage 3 cancer encompasses T groupings of T0, T1, T2, T3, and T4. A tumor with a grouping of T4 measures larger than a T3 grouping and picks up at the value where the maximum T3 measurement left off. A grouping of T4 usually does not contain a maximum tumor measurement because it is the highest T value in the TNM system. Most forms of stage 3 cancer have N groupings of N1, N2, and N3. Cancer that has an N2 grouping have spread into more lymph nodes than what is defined as cancer with an N1 grouping, but contains an upper limit value. A tumor with an N3 grouping means cancer has spread into an extensive number of lymph nodes compared to an N2 grouping, and is the maximum N grouping value. The M grouping in the majority of stage 3 cancers remains at M0. The most common TNM groupings considered to be stage 3 cancer are T0-N2-M0, T1-N2-M0, T2-N2-M0, T3-N1-M0, T3-N2-M0, T4-any N value-M0, and any T value-N3-M0.
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Stage 4
Stage 4 cancer refers to a malignancy that has spread to another organ or distant area in the body regardless of the diameter measurement of the primary tumor and number of lymph nodes that may or may not be involved. Once cancer has been detected in another organ or tissue that does not neighbor the primary tumor, it is referred to as metastatic cancer or secondary cancer. Metastatic cancer is described as having a grouping of M1 instead of M0, like all other cancer stages. There are no M grouping values that exceed M1. The most common organs and distant tissues affected by secondary cancer are the lungs, liver, bones, brain, skin, breast, spine, and thyroid gland. In technical terms, stage 4 cancer has a TNM grouping that includes any T value in combination with any N value, and M1. A common misconception regarding stage 4 cancer is that all forms of stage 4 cancer are terminal. While the combined five-year post-diagnosis survival rate is low for all stage 4 cancers, individual circumstances determine a patient's prognosis. Cancer staging does not always exactly correspond with how curable a patient's cancer is. For example, a large amount of cancer that can be easily removed may have the same prognosis as a small quantity of cancer that is very difficult to remove.
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The TNM System Descriptions
The TNM system is a standard and universal system utilized by medical professionals to describe the severity and spread of malignancy in an individual's body. The International Union Against Cancer and the American Joint Committee On Cancer are credited for the creation of the TNM system. The TNM system is widely accepted internationally for most cancers involving solid tumors, but does not apply to tumors of the central nervous system and leukemia. The alphanumeric code that describes the size of a primary tumor and whether or not it has metastasized is T. N is the alphanumeric code that describes cancer when any regional or neighboring lymph nodes are affected. M is the alphanumeric code that describes when an individual's cancer has spread from one part of their body to another or exhibits distant metastasis. Each letter of the TNM system is accompanied by a number describing the extent of the tumor concerning that particular description.
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Other Staging Factors
Other factors are considered when an oncologist stages a patient's cancer aside from if and how far it has spread beyond its original location. The type of cell affected by cancer is also considered, as different tissues in the body undergo the process of cancer in different ways. A cancerous tumor may be graded using a numeric character between one and four. This grading of a tumor is based on how the cells comprised within it appear underneath a microscope. A lower grade of cancer is associated with cancerous cells that most closely resemble healthy cells, while a high grade of cancer is associated with cancerous cells that are more dissimilar to healthy cells. Some cancers are described by a general and basic staging method that uses roman numerals to describe the size and progression of cancer. The basic and general staging method may also consist of the letters A, B, or C to further characterize the roman numeral categories.
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Other Staging Systems Used
The TNM cancer staging system is not the only staging system used to classify the severity and extent of cancer. The Ann Arbor staging classification is a system commonly utilized to stage lymphomas. Types of cancer that affect the cervix, ovaries, vulva, uterus, and vagina are staged using another cancer staging system closely based on the TNM staging system. This system was created by the International Federation of Gynecology and Obstetrics or FIGO. Another widely known and used system for cancer staging is referred to as summary staging. Summary staging applies to numerous types of cancer and categorizes cancer into five different categories. These categories include in situ, localized, regional, distant, and unknown. Cancer staging systems are known to evolve and change over time due to the new developments and discoveries that allow scientists and the medical community to learn more about cancer.
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Clinical Stage
When an individual is initially diagnosed with cancer, they will receive a stage classification before the start of any cancer treatment. This is referred to as the clinical stage. Cancer in the body will always be referred to using the stage it was assigned when the patient was first diagnosed with the disease, regardless of its progression pattern or metastasis. As more information is gathered about a patient's cancer over time, new alphanumeric characters or medical terms are added onto the initial stage designation they received. The reason for this consistency among cancer staging is to keep the statistical numbers, information, and treatment outcomes for specific cancer types consistent. Using the clinical stage assigned to the patient's cancer can help medical health care providers research and exchange a patient's information and gives them a universal terminology for a consistent understanding, evaluation, and analysis of clinical trial results.
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Pathologic Stage
When an individual is diagnosed with cancer, they will undergo imaging testing and physical examinations to help their physician determine the clinical stage of their cancer. After these tests are done, the patient works with their health care provider to set up a treatment plan. Most solid tumor cancer types are treated with a surgical procedure to remove as much of the cancerous tissue as possible. At the time of the surgical procedure, tissues are taken from the patient's tumor and sent to a laboratory for further examination. The stage assigned based on the information about how the cancerous cells appear underneath a microscope at this point is referred to as the pathologic stage. Some patients do not immediately undergo a surgical procedure to remove the malignant growth, but will still be assigned a pathologic stage based on a non-surgical biopsy performed on their tumor.