Staging is
the process of finding out how far a cancer has spread. The extent of
spread of stomach cancer is an important factor in choosing treatment
options and predicting a patient’s outlook for survival (prognosis).
The tests described above (in the section "How
Is Stomach Cancer
Diagnosed?") are the ones used to determine the stage of the
cancer.
A staging system is a way for members of the cancer care team to
describe the extent of a cancer's spread. The stage of a cancer can be
determined by the information gathered before surgery (clinical stage)
or from the results of the surgery after looking at the removed tissues
(pathologic stage). The stages described below are the pathologic
stages, determined by the results of surgery.
The American Joint Committee on Cancer
(AJCC) TNM System
The system most often used to stage stomach cancer in the United States
is the American Joint Commission on Cancer (AJCC) TNM system. The TNM
system for staging contains 3 key pieces of information:
- T describes
the extent of the primary
tumor (how far it has grown
into the wall of the stomach and into nearby organs).
- N
describes the spread to nearby (regional) lymph nodes.
- M
indicates whether the cancer has metastasized
(spread) to other organs
of the body. (The most common sites of distant spread of stomach cancer
are the liver, the peritoneum (the lining of the space around the
digestive organs), and distant lymph nodes. Less common sites of spread
include the lungs and brain.)
Numbers or letters appear after T, N, and M to provide more
details
about each of these factors:
- The numbers 0 through 4 indicate increasing
severity.
- The letter X means "cannot be assessed" because the
information is
not available.
- The letters "is" mean "carcinoma in situ," which means the
tumor is
contained within the top layer of mucosa cells and has not yet invaded
deeper layers of tissue.
T Categories of Stomach Cancer
The T category describes how far down
through the stomach layers the cancer has invaded. To recall, the
stomach is made of 5 layers. Starting from the inside and working our
way out, the innermost layer is the mucosa. This is
where stomach acid
and digestive enzymes are made. Next is a supporting layer called the
submucosa.
This is surrounded by the muscularis,
a layer of muscle that
moves and mixes the stomach contents. The next 2 layers, the subserosa
and the outermost serosa
act as wrapping layers for the stomach.
- TX:
The main tumor cannot be assessed
- T0:
No evidence of a main tumor
- Tis
(carcinoma in situ): Cancer cells are limited to the
mucosa
(innermost layer of the stomach) and have not invaded deeper layers of
the stomach
- T1:
Tumor invades below the mucosa, into the connective tissue
(lamina propria) or submucosa
- T2:
Tumor invades the muscularis (T2a) or tumor invades the subserosa
(T2b)
- T3:
Tumor invades the serosa, but doesn't invade any nearby organ
- T4:
Tumor goes through the serosa and invades a nearby organ (spleen,
intestines, pancreas, kidney, etc.) or other structures such as major
blood vessels
N Categories of Stomach Cancer
- NX:
Regional lymph nodes cannot be
assessed
- N0: No
spread to nearby (regional) lymph nodes
- N1:
The cancer has spread to 1 to 6 nearby lymph nodes
- N2:
The cancer has spread to 7 to 15 nearby lymph nodes
- N3:
The cancer has spread to more than 15 nearby lymph nodes
M Categories of Stomach Cancer
- MX:
Spread to distant organs cannot be assessed
- M0:
No distant metastasis
- M1:
Distant metastasis (spread of the cancer to tissues or organs far
away from the stomach)
TNM Stage Grouping
The T, N, and M categories
are combined and expressed as a stage, using Roman numerals I through
IV. This is known as stage grouping.
Stage 0: Tis, N0, M0:
This is cancer in its earliest stage. It has not
grown beyond the inner layer of cells that line the stomach. This stage
is also known as carcinoma in situ.
Stage IA: T1, N0, M0:
The cancer
has invaded beneath the mucosa into the connective tissue (lamina
propria) or the submucosa. But it has not grown into the main muscle
layer of the stomach, called the muscularis. The cancer has not spread
to any lymph nodes or anywhere else.
Stage IB: Two
combinations of T and N features are assigned to this
stage.
- T1, N1, M0:
Just as in stage IA, the cancer has grown into the
connective tissue (lamina propria) or submucosa but it has not grown
into the muscularis, the main muscle layer of the stomach. It has also
spread to as many as 6 lymph nodes near the stomach, but not to any
other tissues or organs.
- T2a/b, N0,
M0: The cancer has grown into the main muscle layer of
the
stomach wall, called the muscularis, and may have grown into the
subserosa. It has not spread to any other tissues or organs and has not
spread to any lymph nodes.
Stage II:
Three combinations of T and N features are assigned to this
stage.
- T1, N2, M0:
The cancer has invaded beneath the mucosa into the
connective tissue (lamina propria) or the submucosa. It has not grown
into the main muscle layer, but it has spread to between 7 and 15 lymph
nodes near the stomach.
- T2a/b, N1, M0:
The cancer has grown into the main muscle layer and
may have grown into the subserosa. It has not spread to any nearby
tissues or organs, but it has spread to 1 to 6 lymph nodes near the
stomach.
- T3, N0, M0:
The cancer has grown through all the layers to the
outside the stomach. It has not spread to any nearby tissues or organs
and it has not spread to any lymph nodes.
Stage IIIA:
Three combinations of T and N features are assigned to this
stage.
- T2a/b, N2, M0:
The cancer has grown into the main muscle layer and
may have spread into the subserosa. It has not spread to any nearby
tissues or organs, but it has spread to between 7 and 15 lymph nodes
near the stomach.
- T3, N1, M0:
The cancer has grown completely through all the layers to
the outside of the stomach. It has not spread to any nearby tissues or
organs, but it has spread to between 1 and 6 lymph nodes near the
stomach.
- T4, N0, M0:
The cancer has grown completely through the stomach wall
and into other nearby organs, such as the spleen, intestines, kidneys,
or pancreas. It has not spread to any lymph nodes.
Stage IIIB: T3,
N2, M0: The
cancer has grown completely through all the
layers to the outside of the stomach. It has not spread to any nearby
tissues or organs, but it has spread to between 7 and 15 lymph nodes
near the stomach.
Stage IV:
Three combinations of T, N, and M features are assigned to
this stage.
- T4, N1-3, M0:
The cancer has grown completely through the stomach
wall into other nearby organs, such as the spleen, liver, intestines,
kidneys, or pancreas. It has also spread to nearby lymph nodes, but it
has not spread to distant organs.
- T1-3, N3, M0:
The cancer has spread to more than 15 lymph nodes, but
it has not spread to distant organs.
- Any T, any N,
M1: The cancer has spread to distant organs such as the
liver, lungs, brain, or bones.
If you have any questions about the
stage of your disease, ask your doctor to explain this to you. The
stage of a stomach cancer is an important factor, but it is not the
only factor in considering treatment options and in predicting outlook
for survival.
Five-Year Survival Statistics by Stage
The 5-year
survival rate
refers to the percentage of patients who live
at least 5 years after their cancer is diagnosed. Of course, some
people live much longer than 5 years. Five-year rates are used as a
standard way of discussing prognosis. The 5-year relative survival rate
compares the observed survival of people with stomach cancer to that
expected for people without stomach cancer. Therefore, relative
survival mainly talks about deaths from stomach cancer; it tries to
exclude people with stomach cancer who might die from other causes.
This is thought to be a more accurate way to describe the outlook for
patients with a certain type and stage of cancer.
The overall 5-year
relative
survival rate of all people with stomach cancer in the United
States is about 24%. This survival rate has improved only slightly in
the last 20 years. One reason for this is that most stomach cancers in
the United States are diagnosed at an advanced rather than an early
stage. The stage (extent) of the cancer has a major effect on a
patient's prognosis (outlook for survival).
Another important factor is
the location of the cancer. The 5-year survival rate for cancers of the
distal stomach (the lower portion of the stomach) is higher than for
cancers in the proximal stomach (the upper portion of the stomach). It
is important to remember that statistics on cancer survival are
averages. The outlook for any individual patient can't be predicted
with certainty, and many people survive much longer than would be
expected based on the stage of their cancer.
The 5-year relative survival rates for stomach cancer by stage are as
follows:
| Stage 0: |
77% |
| Stage
IA: |
66% |
| Stage
IB: |
57% |
| Stage
II: |
35% |
| Stage
IIIA: |
17% |
| Stage
IIIB: |
12% |
| Stage
IV: |
3% |
These numbers come from the American College of Surgeons
National
Cancer Data Base and refer to more than 11,000 patients who were
treated in 1998. Because these numbers are several years old, outcomes
for people diagnosed with stomach cancer today may be better.
Revised: 04/23/2007
|