Stomach cancer, like all types of cancer, has several stages of progression¹. Staging helps define and describe the extent of cancer, how far it has spread, and what the best treatment options are likely to be. Each stage is based on specific benchmarks that are determined using a variety of clinical and pathological tests employed by doctors.
While all stomach cancers progress through the stages, some cases may be more aggressive than others. Understanding the stages of stomach cancer and how they are diagnosed is critical for a patient to understand their outlook and the likely treatment options.
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For stomach cancer, there is a nearly universally accepted methodology to staging. The TNM staging system² designed by the American Joint Committee on Cancer (AJCC) is applied to all stomach cancers, except those that start in the cardiac (the top part of the stomach) or gastroesophageal junction, as those are commonly staged as esophageal cancer rather than stomach cancer.
The TNM system relies on rating three distinct traits of cancer (denoted by the acronym TNM) to rate the overall progression. Each factor is assigned a score with higher ratings indicating more serious progression, and then a formula is employed to convert the score into stage 0-IV. The factors involved in the TNM staging system are:
Tumor. This rating measures how far the tumor has grown into the five layers of the stomach wall and if it has permeated any other organs within the body.
(Lymph) nodes. This rating depends on whether cancer has spread into nearby lymph nodes.
Metastasis. Metastasis refers to the spread of cancer, and this rating indicates how much the cancer has spread to other nearby organs and structures within the body.
Once the TNM numbers have been determined, the process that physicians use to assign a stage to the cancer is called stage grouping³. Cancer with the least progression is referred to as Stage 0, or carcinoma in situ. The stages from I to IV indicate an increasing spread of the cancerous cells.
Stage grouping can be done multiple times, and a patient's stage may change as cancer progresses or more reliable staging information becomes available.
Often initial tests will indicate a clinical stage for a patient's cancer, and invasive treatment measures could later reveal a pathological stage that is more informed but different from the initial clinical stage diagnosis.
At first diagnosis, stomach cancer is usually assigned to a clinical stage. This stage grouping is generally derived from clinical tests, physical exams, or imaging results. This stage grouping usually doesn't see the whole picture, but it is a valuable tool to recognize a problem and plan treatment options.
If invasive treatments are used, stomach cancer will eventually be designated with a pathological stage or surgical stage. This is the same stage 0-IV scale as a clinical stage, but it's based on the information obtained in earlier clinical tests and what was revealed by surgery. This usually makes it a much more accurate indicator of cancer’s actual progression.
Sometimes, a pathological stage can actually improve versus the clinical stage, which is often the aim of neoadjuvant treatment. In this treatment plan, doctors will often apply treatments such as chemotherapy or radiation before surgery to improve the chances of successfully excising the tumor. I
n these cases, if the pre-surgery treatment was effective, a pathological stage may become less severe than a clinical stage as more is learned about the treatment results.
There are several tests that doctors use to stage⁴ any particular case of stomach cancer.
The first signs of stomach cancer are usually detected using irregularities in a routine physical exam, combined with information from personal and family medical history.
Information from tests on your blood may indicate the warning signs of stomach cancer, such as anemia that could be caused by bleeding. After these signs are found, other tests may be done to look for other key indicators, such as blood in the stool.
Often when stomach cancer is suspected, an upper endoscopy will be used to gauge the extent of the problem. In this exam, a doctor views the actual tissue of the stomach by inserting a long flexible tube through the esophagus.
A camera at the end of the flexible endoscope allows the physician to search for abnormalities in the stomach tissue to help inform the TNM staging process, and instruments can also be inserted through the endoscope to collect samples of suspect tissue is found.
If nothing abnormal is seen, but a tumor is suspected beneath the surface layer of the stomach, endoscopic ultrasound can get samples from deeper layers of the stomach wall.
One of the most reliable ways to screen for any cancer is with a biopsy. Actually, studying biopsy samples can give physicians insight into where cancer has spread throughout the stomach and rest of the body, which is crucial to determining the stage of stomach cancer.
Biopsy samples can be tested in a number of ways to get more information about the extent of cancer using key indicators in gene and protein changes within the cells. For example, HER2 testing can also strongly indicate what treatments are likely to be effective.
Imaging tests offer a diverse group of tools to give doctors an idea of the metastasis of cancer and the size of tumors in the stomach. Without surgical intervention, these tests often give the best overall look at how far stomach cancer has progressed, and what stage it is in.
Many imaging tests can help to evaluate stomach cancer, including:
Upper gastrointestinal x-ray
Computed tomography (CT) scans
Positron emission tomography (PET) scans
Magnetic resonance imaging (MRI)
Stomach cancer is a complex medical problem, and several types of specialists regularly study and treat it. Typically, a staging and treatment plan will involve a team of physicians for a single patient rather than one dedicated physician.
While any physician may spot the warning signs of stomach cancer that will prompt the staging process, a patient’s treatment team will include the following specialists:
Typically, a gastroenterologist will be involved in the staging process, as they are a doctor who specializes directly in the treatment of the digestive system. Oncologists may use surgery, medications, or radiation as treatment methods, and they will usually collaborate on staging.
Below are the guidelines for classification and descriptions of each stage of stomach cancer according to the TNM system. These guidelines are intended for pathological stages.
If you've received a clinical staging or your treatment plan involves neoadjuvant therapy prior to a pathological staging, there may be differences between the official guidelines and your specific situation that your physician can explain.
It should also be noted that survival rates documented in the SEER database⁵ by the American Cancer Society do not group stomach cancer cases into the TNM stages, even though it is the staging criteria most agreed on by stomach cancer specialists.
Survival rates are instead documented in the SEER database by how far the cancer cells have spread from the point of origin. This translates roughly to the TNM stages but should not be considered concrete data.
Stage I stomach cancer can be divided into two classifications in the TNM system, IA and IB. In both these cases, cancer has not spread to distant parts of the body (M0) but is a growing problem.
Stage IA: (T1, N0, M0). Cancer is detected in the stomach's inner layer (mucosa) but has not yet spread to any lymph nodes.
Stage IB: (T1, N1, M0) or (T2, N0, M0). Cancer has grown into further layers of the stomach (T2) or has spread to one or two lymph nodes (N1).
In the early stages of stomach cancer, it's not uncommon for people to not experience any symptoms⁶ at all. Still, the early development of cancerous cells is usually accompanied by subtle symptoms that may vary from person to person, such as:
Unexplained weight loss
Vague abdominal pain
Decrease in appetite
Bloating or fullness after small meals
Frequent indigestion or heartburn
During stage I, there is a tumor growing in the stomach tissue, and surgery will likely be used to remove affected parts of the stomach. For stage I stomach cancer, you may also commonly receive chemotherapy or radiation therapy as a neoadjuvant treatment before surgical procedures are performed.
For cases where cancer cells are localized entirely within the stomach, and no lymph nodes have been compromised, the relative survival rate for stomach cancer patients is roughly 70%.
In stage II stomach cancer, tumors have grown larger, and cancerous tissue has spread further, but still has not affected other organs (M0). This stage is also further divided into stage IIA and stage IIB.
Stage IIA: (T1, N2, M0), (T2, N1, M0), or (T3, N0, M0). Cancer has grown into deeper muscular layers of the stomach (T2), or the layers of connective tissue outside the stomach (T3). In some cases, it has spread to 1-2 lymph nodes (N1) or as many as 6 (N2).
Stage IIB: (T1, N3a, M0), (T2, N2, M0), (T3, N1, M0), or (T4a, N0, M0). Cancer has spread to as many as 15 lymph nodes (N3a), or the tumor has penetrated through the connective tissue and muscle outside the stomach (T3) or has even spread to the peritoneal lining or serosa.
As with stage I stomach cancer, the symptoms in stage II may prove to be subtle in some patients, and more extreme in others and frequently include:
Uncontrollable weight loss
Persistent abdominal pain
Decrease in or total loss of appetite
Fullness after eating or drinking small amounts
Near constant indigestion or heartburn
The tumor has likely spread beyond the mucosa at this stage but has not spread to other organs. Surgery to remove part of the stomach and any affected lymph nodes is still typically the best treatment in this stage.
It is more likely that this stage of stomach cancer will involve aggressive chemotherapy and radiation therapy before and after surgery.
As more structures outside the stomach are compromised, the relative survival rate decreases to the regional rate of 32% over a five-year period. Those with stage II stomach cancer are likely between this number and the localized rate of 70%, depending on how many structures outside the stomach cancer has spread to.
Stage III stomach cancer represents further penetration through the stomach, and progressively more lymph nodes become compromised. Stage III stomach cancer covers a massive range of TNM scores, divided into stages IIIA, IIIB, IIIC.
Stage III stomach cancer is the most severe staging that still represents no spread to other organs and structures throughout the body, so it covers a wide range of more severe cases than stage II, but still is rated at M0 in the staging process.
In stage III, symptoms are usually much more acute than in the early stages and commonly include:
Uncontrollable weight loss
Frequent and uncontrollable vomiting
Total loss of appetite
Significant abdominal pain
In stage III of stomach cancer, cancer has spread to most if not all of the stomach. The most likely treatment option is the removal of your entire stomach before cancer can spread any further if you are well enough for such a drastic procedure. It is likely that chemotherapy and radiation therapy will also play a key role in your long-term treatment plan.
Stage III cancer has, in nearly every circumstance, started to spread beyond the barriers of the stomach. Based on the numbers provided in the SEER database, those at this stage will have roughly a 32% five-year survival rate.
Stage IV is the highest stage for stomach cancer. A case is considered to have stage IV stomach cancer when cancer has spread to parts of the body beyond the area immediately surrounding the stomach (M1). Any metastasis rating beyond 0 using the TNM system is classified as stage IV stomach cancer, so any different T and N values are possible with this stage.
As stage IV implies that cancer has spread beyond just the stomach, many more potential symptoms could be caused by other major organs being compromised. While these may vary, the consistent symptoms of a growing stomach tumor in later stages often include:
Inability to maintain weight without medical intervention
Constant abdominal pain
Bloating of the stomach from fluid build-up (ascites)
At stage IV, stomach cancer has spread to other parts of the body and is a systemic problem throughout the body. Treatment plans at this stage will vary, but stage IV cancer will be much harder to remove entirely from the body, and treatment will often focus on managing cancer's effect on your body and relieving symptoms as well as fighting further spread.
As a growing tumor compromises more of your GI tract, further surgeries like stents or gastric bypass may be necessary.
It should be noted that medical advances are always an ongoing process, and new treatments are identified through clinical trials and other breakthroughs every day.
Once stomach cancer has moved beyond the stomach into other major organs throughout your body, it can be much harder to control its spread.
Patients in this stage fall into the "distant" metastasis category in the SEER database and are projected to have a 6% five-year relative survival rate.
Like other types of cancer, stomach cancer is categorized by stages based on how far it has spread and the growth of any tumors.
Almost universally, oncologists and gastroenterologists use the TNM staging system to determine the stage of stomach cancer by using a wide variety of tests to gauge cancer's progression.
The stage of a particular case of stomach cancer is dependent on several variables, but with the increasing number of stages, the symptoms of cancer will often become more severe, as will the outlook and potential survival rate for a patient.
Effective stomach cancer treatments rely heavily on early diagnosis, as cancer caught in earlier stages offers a far more promising outlook.
Stomach Cancer: Stages | Cancer.Net
Stomach Cancer Stages | American Cancer Society
Tests for Stomach Cancer | American Cancer Society
Stomach Cancer Survival Rates | American Cancer Society
Stomach Cancer Symptoms | Stanford Health Care