Screening and Staging

Once you’re diagnosed with cancer, your doctor will probably discuss with you the stage of your cancer, which can range from early stage to advanced. Staging describes the extent of tumor growth and detectable spread to another tissue or organ as well as the severity of the cancer based on its growth and spread. This information is then used to guide your treatment.

Overview

Basically, early stage cancers (that is, stage I) can often be treated with only one or two types of treatment (surgery and/or radiation therapy), whereas more advanced or aggressive tumors (stage III) require more intensive therapy involving combinations of three or more types of treatment, such as surgery combined with chemotherapy and radiation therapy. In other words, the treatment intensity is geared to the type of cancer and its stage in order to get the best results.

Knowing the stage of your cancer helps your doctor plan your multidisciplinary treatment and estimate the course of the disease as well as the likely outcome of treatment. Detecting cancer in its earliest stages is important because it means that treatment may be simpler and have a better outcome, or prognosis, compared to cancer that has spread to regional lymph nodes or distant organs in its later stages. In the later stages, a cure can still be achieved but it will require more intensive and combined treatments of surgery, drugs, and radiation therapy.

Cancer staging is based on clinical, radiologic, and pathologic evaluations that determine how large and aggressive the original cancer is and whether it has invaded surrounding tissues and organs or spread through the bloodstream or lymphatic system.

Staging considers the location, size, and aggressiveness of your tumor, the number of tumors you have, whether the primary tumor has spread to your lymph nodes, the types of cancer cells in your tumor, and whether the cancer has metastasized (spread) to other parts of your body.

Basically, cancers can be divided into five main categories:

  • In situ, meaning early cancer that is present only in the layer of cells in which it began.
  • Regional, meaning the cancer has spread to nearby lymph nodes, organs, or tissues.
  • Unknown, meaning there is not enough information to designate a stage or know where an advanced cancer originated.

TNM System

All cancer specialists use a cancer staging system that is standardized by experts in the American Joint Committee on Cancer (AJCC), called the TNM system. TNM uses a shorthand method for describing the extent or size of the tumor (T), the presence and extent of tumor spread to the regional lymph nodes (N), and whether the tumor has metastasized to an organ or tissue outside the region where it originated (M).

To further subdivide cancers into categories that reflect the increasing size of the tumor and extent of spread, a number is added to the letters T, N, and M. For example, a breast tumor designated T2, N1, M0 is one that measures between 2 and 5 cm across (about 1 to 2 inches) and has spread from the breast to lymph nodes in the armpit, but not to other parts of the body. This combination would be designated as stage II breast cancer, with an associated 5-year survival rate ranging from 81% to 92%. For virtually all cancers, these combinations of letters and numbers correspond to one of five stages, as shown in the following Stages of Cancer table.

Stages of Cancer

Stage Definition
Stage 0 Carcinoma in situ (literally means: “cancer in place”). The cancer cells have not yet invaded into surrounding tissues; without invasion the tumor can’t spread and the cure rate is 100%.
Stage I The primary tumor is small but invasive into surrounding tissues and has not spread.
Stage II
The primary tumor is larger, but there is still no clinical evidence of spread.
Stage III
The tumor has spread to lymph glands (also called lymph nodes) in that region of the body.
Stage IV
The cancer has spread beyond the region where it initiated to a distant tissue or organ.

 

Three stages of colon cancer as the cancer cells divide and the tumor grows. In stage I, the tumor is small and has not penetrated the layer of cells lining the colon. In stage II, the tumor has penetrated the muscle wall of the colon. In stage III, the tumor has spread to nearby lymph nodes. Source: Medline Plus, a service of the U.S. National Library of Medicine and the National Institutes of Health.

The above figure also illustrates the progressive spread of an intestinal cancer and its invasion into surrounding tissues.

Virtually all cancer specialists use the staging definitions described above, but not all types of cancers receive TNM designations, usually because their mode of spread doesn’t involve regional lymph glands (for example, leukemias and some childhood cancers) or they are life threatening because of their origin (for example, in the brain and spinal cord).

Tests Used

To determine the stage of your cancer, your doctor will give you a thorough physical exam by looking, listening, and feeling for anything abnormal in your body. The physical exam may help your doctor determine the location and size of your tumor and whether it has spread.

Your doctor will also order imaging studies, such as x-rays of the chest or abdomen, CT (computed tomography) scans, PET (positron emission tomography) studies, and MRI (magnetic resonance imaging) scans, to help determine the size, location, and possible spread of your cancer. In some circumstances, your doctor may need to look inside an organ with lighted, flexible tubing called an endoscope to visualize and biopsy (removal of cells from a suspicious growth abnormalities in the intestinal tract, lungs, or other internal organs.)

Laboratory tests may be needed of your blood, urine, body fluids, and tissues to look for biological markers of tumors. Your doctor may also order a biopsy so a pathologist can look at the cells under a microscope to determine if the growth is cancerous and, if so, its stage of development. Many biopsies are performed with a needle, although some situations require that a piece or all of the tumor be removed surgically to determine a diagnosis.

 



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