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Staging is
the process of finding out how much cancer there is in the body and
where it is located. It is how the doctor learns the stage of a
person's cancer. Doctors use this information to plan treatment and to
help find out a person's outlook (prognosis). Cancers with the same
stage usually have similar outlooks and are often treated the same way.
The cancer stage is also a way for doctors to describe the extent of
the cancer when they talk with each other about a person's
case.
Why is staging needed?
Doctors need to know the amount of cancer and where it is in
the body to make sure a person gets the best possible treatment. For
example, the treatment for early stage breast cancer may be surgery and
radiation, while a more advanced stage of breast cancer may need to be
treated with chemotherapy, too. Doctors also use the stage to help
predict the course a cancer is likely to take.
What is the doctor looking for when staging
cancer?
For most cancers, the stage is based on 3 main factors:
- the original (primary) tumor's size and whether or not the
tumor has grown into nearby areas
- whether or not the cancer has spread to the nearby lymph
nodes
- whether or not the cancer has spread to distant areas of
the body
Some cancers of the blood, such as leukemias, are not staged
in this way because they are assumed to be in all parts of the body.
Cancers in or around the brain are also not staged using the TNM
system, since these cancers can disrupt vital brain and body functions
before they even begin to spread.
What does staging involve?
Doctors gather different types of information about a cancer
to figure out its stage. Depending on where the cancer is located, the
physical exam may give some clue as to the extent of the cancer.
Pictures taken during tests like x-rays, CT scans, and MRIs may also
provide information about how much and where cancer is in the body.
Taking out tumors or pieces of tumors and looking at them under the
microscope (biopsy) is needed to confirm the diagnosis of cancer, but
it can also help stage the cancer. Samples can be removed either during
surgery or during less invasive biopsy procedures. The different
techniques used to remove and examine samples are described in our Surgery
document.
Types of staging
There are different types of staging.
Clinical staging
is done at the time of diagnosis, before any treatment is given. It is
an estimate how much cancer there is based on the physical exam,
imaging tests (x-rays, CT scans, etc.), and sometimes biopsies of
affected areas. For some cancers the results of other tests, such as
blood tests, are also used in staging. The clinical stage is a key part
of deciding the best treatment to use. It is also the baseline used for
comparison when looking at the cancer's response to treatment.
Pathologic
staging can only be done on patients who have had surgery
to remove the cancer or to look at how much cancer is in the body. It
combines the results of clinical staging with the results from the
surgery. In some cases, the pathologic stage may be different from the
clinical stage (for example, if the surgery shows the cancer has spread
more than it was thought to have spread before surgery). The
pathological stage gives the health care team more precise information
that can be used to predict treatment response and outcomes
(prognosis).
Restaging
is not common, but it may be done to find the extent of the cancer if
it comes back (recurs) after treatment. This is done to help decide
what the best treatment option would be at this time. Restaging is
discussed further in the section "A cancer's stage does not change."
The TNM staging system
At one time there were many different systems used to stage
cancers, and sometimes different systems were used to stage the same
type of cancer. But many of these systems did not give doctors very
useful information.
The American Joint Committee on Cancer (AJCC) developed the TNM classification system
as a tool for doctors to stage different types of cancer based on
certain standards. It has replaced many of the older staging systems.
In the TNM system, each cancer is assigned a T, N, and M category.
The T
category describes the original (primary) tumor. The tumor size is
usually measured in centimeters (2 and 1/2 centimeters is about 1 inch)
or millimeters (10 millimeters = 1 centimeter).
- TX
means the tumor can't be measured.
- T0
means there is no evidence of primary tumor (it cannot be found).
- Tis
means the cancer is in situ (the tumor has not started growing into the
structures around it).
- The numbers T1,
T2, T3, and T4 describe the
tumor size and/or level of invasion into nearby structures. The higher
the T number, the larger the tumor and/or the more it has grown into
nearby tissues.
The N category
describes whether or not the cancer has spread into nearby lymph nodes.
- NX
means the nearby lymph nodes cannot be evaluated.
- N0
means nearby lymph nodes do not contain cancer.
- The numbers N1,
N2, and N3 describe the
size, location, and/or the number of lymph nodes involved. The higher
the N number, the more the lymph nodes are involved.
The M category tells whether there are distant metastases
(spread of cancer to other parts of body).
- MX
means metastasis can't be evaluated.
- M0
means that no distant metastases were found.
- M1
means that distant metastases were found (the cancer has spread to
distant organs or tissues).
Each cancer type has its own version of this classification
system, so letters and numbers don't always mean the same thing for
every kind of cancer. For example, for some cancers, classifications
may have subcategories, such as T3a and T3b, while others may not have
an N3 category.
Stage grouping
Once the T, N, and M have been learned, they are combined, and
an overall "stage" of 0, I, II, III, or IV is assigned. (Sometimes
these stages are subdivided as well, using letters such as IIIA and
IIIB.)
For example, a T1, N0, M0 breast cancer would mean that the
primary breast tumor is less than 2 cm across (T1), does not have lymph
node involvement (N0), and has not spread to distant parts of the body
(M0). This would make it a stage I cancer.
A T2, N1, M0 breast cancer would mean that the cancer is more
than 2 cm but less than 5 cm across (T2), has reached only the lymph
nodes in the underarm area (N1), and has not spread to distant parts of
the body. This would make it a stage IIB cancer.
Stage 0 is carcinoma
in situ for most cancers. This means the cancer is at a
very early stage, is only in the area where it first developed, and has
not spread. Not all cancers have a stage 0. Stage I cancers are the
next least advanced and often have a good prognosis (outlook for
survival). As the stage number goes up the cancers are more advanced
(bigger and more widespread), but in many cases they can still be
treated.
Other staging systems
Staging systems other than the TNM system are often used for
Hodgkin disease and other lymphomas, as well as for some childhood
cancers. The International Federation of Gynecologists and
Obstetricians (FIGO) has a staging system for cancers of the female
reproductive organs. The TNM stages closely match the FIGO stages,
which makes it fairly easy to convert stages between these 2 systems.
Other, older staging systems (such as the Dukes system for
colorectal cancer) may still be used by some doctors. If your doctor
uses another staging system, you may want to find out if the stage can
be converted into the TNM system. This will often help if you want to
read more about your cancer and its treatment, since TNM is more widely
used.
A cancer's stage does not change
An important point some people have trouble understanding is
that the stage of a cancer does not change over time, even if the
cancer progresses. A cancer that comes back or spreads is still
referred to by the stage it was given when it was first found and
diagnosed.
For example, if a woman were first diagnosed with "stage II
breast cancer" and the cancer went away with treatment but now has come
back and spread to the bones, the cancer is called "stage II breast
cancer with recurrent disease in the bones." If the breast cancer did
not respond to treatment and spread to the bones it is called "stage II
breast cancer with metastasis in the bones." In either case, the
original stage does not change and this is not called "stage
IV breast cancer." A stage IV breast cancer refers to a cancer that has
already spread to a distant part of the body when it is first
diagnosed. A person keeps the same diagnosis stage, but more
information is added to the diagnosis to explain the current disease
status.
This is important to understand because survival statistics
and information on treatment by stage for specific cancer types refer
to the stage when the cancer was first diagnosed. The survival
statistics related to stage II breast cancer that has recurred in the
bones may not be the same as the survival statistics for stage IV
breast cancer.
Still, restaging may be done to measure the cancer's response
to treatment or to assess cancer that has come back (recurred) and will
need more treatment. This often means going through the same process
that was done when the cancer was first diagnosed: exams, imaging
tests, biopsies, and possibly surgery to restage the cancer. If the
cancer is restaged, the stage will be recorded with a lower-case "r"
before the restaged categories. A restaging process that finds T2, N3,
M1, for instance, would be written rT2, rN3, rM1. The stage grouping IV
would be written stage rIV rather than stage IV, to note that it is
different from the stage at diagnosis. The original stage at diagnosis
always stays the same. Restaging is not often done in cancer treatment,
but it is more common in clinical trials.
What else can affect prognosis?
Your outlook (prognosis) is affected by the type of cancer you
have, but it is also strongly affected by the cancer's stage. For some
cancers, another important factor that is considered along with stage
is tumor grade.
Grade
Tumor grade describes how different the cancer cells look when
compared to normal ones. The grade is assigned after the doctor looks
at a biopsy of the cancerous tissue.
Tumor grade is taken into account when making treatment
decisions and is another factor that affects prognosis for some kinds
of cancer. The grade of the cancer reflects how abnormal the cancer
cells look under the microscope. Grading is done by a pathologist who
compares the cancer cells from the biopsy to how normal cells look in
the same area. (A pathologist is a doctor who is specially trained in
diagnosis and classification of diseases by lab tests, such as looking
cells under a microscope.) Grade is important because cancers with more
abnormal-looking cells tend to grow and spread faster. Higher grade
cancers (meaning that the cancer cells look very different from normal
cells) usually have a worse prognosis, and sometimes need different
treatments.
The American Joint Committee on Cancer (AJCC) recommends the
following cancer grading classifications:
- GX
Grade cannot be assessed
- G1
Well-differentiated (the cancer cells look a lot like normal cells)
- G2
Moderately well-differentiated (cancer cells look somewhat like normal
cells)
- G3
Poorly differentiated (cancer cells don't look much like normal cells)
- G4
Undifferentiated (the cancer cells don't look anything like normal
cells)
The lower the cancer grade the better the prognosis. G1
cancers are linked to the best outcomes. G4 is linked to the worst
outcomes, and G2 and G3 fall in between.
There are problems with grading, though. For example, many
different grade levels may be found in one tumor or the tumor grade may
change with time.
There are also several grading systems for different types of
cancer, such as the Gleason grades for prostate cancer or the Kernohan
grades for brain tumors. Each grading system divides cancer cells into
those with the most abnormal cells, the least abnormal cells, and those
in between. Generally, whatever grading system is used, the lower
numbers indicate less aggressive cancers while the higher numbers
suggest faster cancer cell growth and spread.
Along with stage and grade, your outlook is also influenced by
the treatment you get, your general health, and many other factors that
your doctor will take into account.
Finding out more about your type of cancer
If you are looking for details on staging or grading for a
certain type of cancer, you can find this information in each of our
documents on specific cancer types. You can get any of these cancer
site documents on our Web site or by calling our toll-free number
below.
Additional resources
More information from your American Cancer
Society
The following related information may also be helpful to you.
These materials may be ordered from our toll-free number,
1-800-ACS-2345.
- After Diagnosis: A Guide for Patients and Families (also
available in Spanish)
- Surgery
(also available in Spanish)
National organizations and Web sites*
In addition to the American Cancer Society, other sources of
patient information and support include the following:
National Cancer Institute
Toll-free number: 1-800-4-CANCER (1-800-422-6237)
Web site: www.cancer.gov
*Inclusion on this list does not imply endorsement by the
American Cancer Society.
No matter who you are, we can help. Contact us anytime, day or
night, for cancer-related information and support. Call us at 1-800-ACS-2345 or
visit www.cancer.org.
References
Greene FL, Page DL, Fleming ID, Fritz AG, Balch CM, Haller DG,
Morrow M, eds. American Joint Committee on Cancer Staging Manual. 6th
ed. New York, NY: Springer; 2002.
Yarbro CH, Frogge MH, Goodman M, Groenwald SL, eds. Cancer
Nursing Principles and Practice. 5th ed. Sudbury, MA: Jones and
Bartlett Publishers, Inc. 2000.
Revised: 04/23/08
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