Gastric adenocarcinoma is the most prevalent form of stomach cancer, originating from the gastric epithelium. This cancer begins in the mucus-producing cells that form the innermost lining of the stomach, known as the mucosa. These glandular cells produce mucus and other fluids that aid in digestion.
This cancer is categorized into two primary types by location: gastric cardia cancer, which develops in the top portion of the stomach where it connects to the esophagus, and non-cardia gastric cancer, in all other areas. Under a microscope, these cancers can also be described as intestinal or diffuse. Intestinal-type adenocarcinomas have cells that appear similar to normal cells, while diffuse-type cells are less distinct and tend to be more aggressive.
Causes and Risk Factors
The development of gastric adenocarcinoma is linked to a combination of environmental and genetic factors. A primary cause is chronic infection with Helicobacter pylori (H. pylori) bacteria, a major contributor to cancers in the lower part of the stomach. This long-term infection can lead to chronic inflammation and atrophic gastritis, a condition where the stomach lining thins, increasing cancer risk.
Dietary habits play a role. High consumption of salted, smoked, or poorly preserved foods is associated with an increased risk, while a diet rich in fruits and vegetables may lower it. Lifestyle choices such as smoking and heavy alcohol consumption also elevate the risk. Smoking, for instance, can double a person’s risk of developing stomach cancer.
Certain medical conditions are also recognized risk factors. These include pernicious anemia, an autoimmune condition affecting vitamin B12 absorption, and a history of stomach surgeries that can alter the stomach’s acidic environment. A small percentage of cases are linked to inherited genetic syndromes, such as Hereditary diffuse gastric cancer (HDGC), which is caused by a mutation in the CDH1 gene.
Symptoms and Initial Detection
Early-stage gastric adenocarcinoma rarely produces noticeable symptoms, often leading to a diagnosis when the disease is more advanced. When symptoms appear, they are often vague and can be mistaken for more common gastrointestinal issues. These initial signs may include:
- Persistent indigestion or heartburn
- A feeling of fullness after eating a small meal
- General discomfort or pain in the upper abdomen
- Persistent nausea
As the tumor grows, symptoms can become more severe. Unexplained weight loss and vomiting are common. Some individuals may experience difficulty swallowing (dysphagia), if the tumor is in the upper part of the stomach. Blood in the vomit or stool, which can make the stool appear black (melena), is a sign of a more advanced tumor.
Fluid buildup in the abdomen (ascites) and yellowing of the skin and eyes (jaundice) can occur if the cancer has spread to other parts of the body, such as the liver. Because many of these symptoms overlap with less serious conditions, it is important to consult a doctor if they are persistent. Screening is not common in Western countries but is practiced in regions with higher incidence rates.
Diagnosis and Staging
Diagnosis begins with an evaluation of the patient’s symptoms and medical history. The primary diagnostic tool is an upper endoscopy (EGD), where a doctor inserts a thin, flexible tube with a camera through the throat to examine the esophagus, stomach, and first part of the small intestine. If suspicious areas are found, a tissue sample (biopsy) is taken for a pathologist to examine for cancer cells.
Once a diagnosis is confirmed, the next step is staging to determine the cancer’s extent. Staging assesses how far the tumor has grown into the stomach wall, whether it has spread to nearby lymph nodes, and if it has metastasized to distant organs. Imaging tests are used for this, including CT scans, PET scans, and endoscopic ultrasound (EUS). A diagnostic laparoscopy, a minimally invasive surgery, may also be used to inspect the abdominal cavity for spread.
This information is used to assign a stage using the TNM (Tumor, Node, Metastasis) system. The “T” describes the tumor’s size and depth of invasion, “N” indicates lymph node involvement, and “M” signifies if the cancer has spread to other parts of the body. This staging, which ranges from stage 0 to stage IV, is used for determining the prognosis and guiding the treatment plan.
Medical Treatment Approaches
Treatment for gastric adenocarcinoma depends on the cancer’s stage at diagnosis. For localized disease, surgery is the principal therapy and offers the best chance for a cure. The most common procedure is a gastrectomy, which removes part or all of the stomach, along with nearby lymph nodes. For very early-stage tumors, a less invasive procedure called endoscopic resection may be an option.
Chemotherapy is a main component of treatment and can be used at various points. It may be administered before surgery (neoadjuvant chemotherapy) to shrink the tumor, or after surgery (adjuvant chemotherapy) to eliminate any remaining cancer cells. For advanced or metastatic cancer, chemotherapy is often the primary treatment, using a combination of drugs.
Radiation therapy uses high-energy rays to destroy cancer cells and is often used with chemotherapy (chemoradiation). Targeted therapies are designed to attack specific molecules on cancer cells, such as in HER2-positive cancers. Immunotherapy harnesses the body’s immune system to fight cancer and is another newer approach used for advanced cases, with checkpoint inhibitors showing promise in certain patients.
Prognosis and Survivorship
The prognosis for gastric adenocarcinoma is closely tied to the cancer’s stage at diagnosis. When detected at an early, localized stage before it has grown through the stomach wall, the outcome is more favorable. The 5-year relative survival rate estimates the percentage of patients likely to be alive five years after diagnosis compared to the general population.
For localized gastric cancer, the 5-year survival rate is significantly higher than for cancers that have spread. For instance, survival rates for stage I cancer can be as high as 94%, while they drop for more advanced stages. If the cancer has spread to regional lymph nodes or metastasized to distant parts of the body like the liver, the prognosis is less favorable. The 5-year survival rate for distant-stage cancer is approximately 5%.
Survivorship involves ongoing care after treatment is completed. This includes regular follow-up appointments and imaging tests to monitor for recurrence. Patients who have undergone a gastrectomy often need to make lifelong dietary changes to manage digestion and nutrient absorption. Managing the long-term physical and emotional effects of treatment is a component of survivorship care.