Introduction
Staging is the process of finding out how much cancer
there is in the body and where it is located. 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 communicate with
each other about a person’s case.
Why Is Staging Needed?
Doctors need to know the amount and location of cancer in the body to
make sure a person gets the proper treatment for his or her specific
cancer. For example, the treatment for early stage breast cancer may be
surgery and radiation, while a more advanced stage of breast cancer may
require treatment with chemotherapy. 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 other 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 not staged using the TNM system,
since these cancers can interfere with vital functions of the brain and
body before they even begin to spread.
What Does Staging Involve?
Doctors gather different types of information about a cancer
to determine its stage. Depending on where the cancer is located, the
physical exam may give some clue as to the extent of the cancer.
Imaging tests such as x-rays, CT scans, and MRI scans may also provide
information about where a cancer may be located in the body. Removing
tumors or pieces of tumors and looking at them under the microscope
(biopsy) often confirms 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 an estimate how much
cancer there is based on the results of the physical exam, imaging
tests (x-rays, CT scans, etc.) and sometimes biopsies of affected
areas. For certain cancers the results of other tests, such as blood
tests, are also used in staging.
Pathologic
staging can only be done on patients who have had surgery
to remove or explore the extent of the cancer. It combines the results
of clinical staging (physical exam, imaging tests, etc.) 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.)
Restaging
is sometimes used to determine the extent of the disease if a cancer
recurs (comes back) after treatment. This is done to help decide what
the best treatment option would be at this time. This type of staging
is not common, as discussed 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. Although some of the better ones are still used, 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 standard criteria. 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 or evaluated.
- T0
means there is no evidence of primary tumor (the primary tumor cannot
be found).
- Tis
means the cancer is in situ (the tumor has not started
growing into the structures around it).
- The numbers T1–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 further it has grown into nearby
structures.
The N
category describes whether or not the cancer has reached
nearby lymph nodes.
- NX
means the nearby lymph nodes can't be measured or evaluated.
- N0
means nearby lymph nodes do not contain cancer.
- The numbers N1–N3
describe the size, location, and/or the
number of lymph nodes involved. The higher the N number, the more 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 measured or evaluated.
- M0
means that no distant metastases were found.
- M1
means that distant metastases were found (the cancer had 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 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 I cancers are the least advanced and often have a better
prognosis (outlook for survival). Higher stage cancers are often more
advanced but in many cases can still be treated successfully.
Other Staging Systems
Staging systems other than the TNM system are often used for
Hodgkin disease and other lymphomas, and 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.
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 diagnosed.
For example, if a woman was first diagnosed with "stage II
breast cancer," but the cancer now has spread to the bones, the cancer
is called "stage II breast cancer with recurrent disease in the bones"
(if the cancer went away with treatment) or "stage II breast cancer
with metastasis in the bones" (if the cancer never went away
completely). This is not "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.
When certain cancers come back, a doctor might restage
the cancer if more treatment is being planned. 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 designation. 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 distinguish it from the stage assigned at diagnosis.
The original stage at diagnosis still stays the same. Restaging is not
often done in cancer treatment, although it is more common in clinical
trials.
Other Factors Also Affect Outlook
Your prognosis is affected by the type of cancer you have, but
it is also strongly influenced by the cancer's stage. For some cancers,
another important factor that is considered along with clinical stage
is tumor grade. The grade is assigned after a
biopsy of the cancerous
tissue has been examined. Tumor grade describes how different the
cancer cells look compared to normal ones.
Grade
Tumor grade is considered 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 normal cells. (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 more quickly. Higher grade cancers (meaning that the
cancer cells look very abnormal) 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 determined
- 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 associated with the
worst outcomes and the others fall in between.
There are problems with grading, though. For example, several
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 more rapid cancer cell growth and spread.
In addition to stage and grade, your outlook is also
influenced by the treatment you receive, your general health, and many
other factors that your doctor will take into account.
If you are looking for details on staging or grading for a
particular type of cancer, this information is contained in each of our
documents on specific cancer types. You can get copies of any of these
cancer site documents by calling our toll free number.
Additional Resources
More Information From Your
American Cancer Society
We have selected some related information that may also be
helpful to you. These materials may be ordered from our toll-free
number, 1-800-ACS-2345.
A Message of
Hope: Coping with Cancer in Everyday Life (also
available
in Spanish)
After
Diagnosis: A Guide for Patients and Families (also
available in Spanish)
Talking
with
Your Doctor (also available in Spanish)
Understanding
Chemotherapy (also available in Spanish)
Understanding
Radiation Therapy (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
Telephone: 1-800-4-CANCER (1-800-422-6237)
Internet Address: www.cancer.gov
*Inclusion on this list does not imply endorsement by
the American Cancer Society.
Please call 1-800-ACS-2345 any time any day you have questions
or need help. The American Cancer Society has information, resources,
and support available on any cancer-related topic.
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.
Updated: 4/05/07
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