Gastric (Stomach) Cancer
by I. Mountzios, M.D., Medical Oncologist

Etiology - Epidemiology

Cancer of the stomach, or gastric cancer, continues to be the second cause of death related to cancer worldwide, following lung cancer. According to the most recent data of the World Health Organization (WHO), approximately 800,000 new cases of gastric cancer and 650,000 deaths are recorded every year worldwide.

Interestingly, the incidence of gastric cancer has significantly decreased in the last few decades, for reasons that are not clear yet and may be related to better conditions of food preservation and elimination of food-related toxins. The high number of new cases in the last few years may be attributed to better recording of new cases and the increasing number of new cases diagnosed by screening gastroscopy or gastroscopy performed for other reasons. 

The incidence of gastric cancer is characterized by wide geographical variation, with the highest frequency in upper East (mainly Japan), Latin America and Eastern Europe, while in India, most countries of Africa and Europe and North America, the incidence is lower. Of note, Japan has ten-times more new cases of gastric cancer annually (77 new cases per 100,000 habitants), as compared to the United States (7.4 new cases per 100,000 habitants).

Etiological factors that have been correlated with gastric cancer include dietary habits, Helicobacter pylori infection and bile reflux. It seems that increased intake of red meat, saturated fatty acids and preservatives containing nitric salts are associated with increased risk for gastric cancer, whereas consumption of fruits and vegetables seems to have a protective effect.  Infection with Helicobacter pylori seems to provoke chronic inflammation (gastritis) that may predispose to cancer, since tha majority of cancer cases, and especially of the “enteric” subtype (see below) are postivie for the infection. Finally, large epidemiological studies have shown that surgical removal of the stomach (gastrectomy) according to a technique called Billroth type 2, is correlated with increased reflux of bile into the remaining stomach and may thus predispose to gastric cancer.

 

Clinical Symptoms

Patients with stomach cancer may experience the symptoms or signs described in this section.

Sometimes, people with stomach cancer do not show any of these symptoms, or, vice versa, these symptoms may be caused by a medical condition that is not cancer. Unfortunately, stomach cancer is usually not found at an early stage because it often does not cause specific symptoms and is usually confused with symptoms of gastritis.

When symptoms do occur, they may be vague and can include:

  • Indigestion or heartburn
  • Pain or discomfort in the abdomen
  • Nausea and vomiting, particularly vomiting up solid food shortly after eating
  • Diarrhea or constipation
  • Bloating of the stomach after meals
  • Loss of appetite
  • Weakness and fatigue
  • Vomiting blood or having blood in the stool
  • Unexplained weight loss
  • Unexpected dislike for eating meat

 

Diagnosis and Staging

Diagnosis of gastric cancer is usually made by endoscopic examination of the stomach, a procedure called gastroscopy. During this procedure, one or more biopsy specimens are obtained from the tumor or the suspicious lesion in the stomach and the material is sent for pathologic examination (examination under microscope). The pathologic examination is the most accurate examination that establishes the diagnosis of gastric cancer.

After a diagnosis of gastric cancer has been established, the next step is staging. Staging is a special procedure comprising a set of tests that allow the doctors to define accurately to what extent has the disease spread into the patient’s body, and contains very important information about the patient’s prognosis and the expected outcome of treatment. Usually, the therapeutic regimen or combination also depends on the stage of the disease at the time of diagnosis.

Other useful tests for the staging of gastric cancer are the following:

  • Computed Tomography (CT) scans of the thorax and the abdomen
  • Magnetic Resonance Imaging (MRI) scans of the thorax and the abdomen when indicated
  • Bronchoscopy (in cases of possible invasion of the trachea by cancer)
  • Endoscopic Ultrasound (very sensitive for the determination of the degree of invasion of the tumor to the stomach wall and the detection of lymph nodes around the stomach that are enlarged because of cancer infiltration)
  • Thoracoscopy-laparoscopy (surgical exploration of the thoracic or peritoneal cavity) is indicated in rare difficult cases
  • PET/CT scan (a very sensitive scan which resembles the CT scan, but allows for better imaging of the tumor by exploiting its increased metabolic activity).

Based on these tests the tumor is usually classified into one of the following four categories:

  1. Stage 1: Tumor restricted to the inner layer (mucosa) of the stomach
  2. Stage 2: Tumor extending in the muscular wall of the stomach
  3. Stage 3: Tumor extending outside the gastric wall and/or invading regional lymph nodes but without distant metastases
  4. Stage 4: Presence of distant metastases (Lung, liver etc).

 

Pathology

According to the World Health Organization (WHO), gastric cancer is the malignant tumor of the adenic epithelium (the inner layer of the stomach called mucosa), which does not include adenocarcinoma of the gastroesophageal junction (the part where the esophagus meets the stomach), as this is usually studied together with esophageal adenocarcinoma.

A gastric tumor may look like a mass, a polyp, an ulcer, or a diffuse lesion that occupies a large portion or even the whole stomach.

Note that, according to the a classification system called "Lauren classification", stomach cancer is characterized by two main histological types, (a) enteric and (b) diffuse. 

  • The enteric type is named like that because the picture of the tumor under the microscope resembles that of the intestinal inner layer (mucosa) and is mainly located in a specific region of the stomach.
  • The diffuse type is mainly  characterized by cancer cells full of mucus (“signet ring cells”) and spreads throughout the gastric wall. These two types have distinct epidemiological, clinical and biological features, with the diffuse type bearing the worse prognosis.

There are rare cases of mixed classification, and of non-classified cancers.

 

Treatment Strategies

Stomach cancer may be treated with surgery, radiation therapy, or chemotherapy. Descriptions of these common treatment options for stomach cancer are listed below. Often, a combination of these treatments is used. It can be difficult to cure stomach cancer because it is often not detected until it is at an advanced stage.

Treatment options and recommendations depend on several factors, including the type and stage of cancer, possible side effects, and the patient’s preferences and overall health conditions.

 

Surgery

Surgery is the removal of the tumor and surrounding tissue during an operation. A surgical oncologist is a doctor who specializes in treating cancer using surgery.

The type of surgery used depends on the stage of the cancer, as well as the location of the primary tumor within the stomach.

If the cancer has spread to the outer stomach wall or to the lymph nodes (stages 2 or 3), surgery plus chemotherapy and/or radiation therapy may be used. The surgeon can perform a subtotal or partial gastrectomy (removal of part of the stomach) or a total gastrectomy (removal of all of the stomach). After this surgery, the patient will only be able to eat a small amount of food at a time.

Sometimes, in case of stage 3, the so-called “locally advanced” disease, it may be preferable to treat the patient with chemotherapy or with combined chemo-radiotherapy, in order to achieve tumor shrinkage and subsequently, total or partial gastrectomy, if feasible.

Gastrectomy is a major surgery and can have serious side effects. One common side effect is a group of symptoms known as “dumping syndrome”, which includes cramps, nausea, diarrhea, and dizziness after eating. This happens when food enters the small intestine too fast. The symptoms usually disappear in a few months, but they may be permanent for some people. Patients who have had their entire stomach removed will need regular injections of vitamin B12 because they will no longer be able to absorb this essential vitamin through their stomach.

 

Surgery for supportive or palliative care

In addition to surgery to treat the disease, surgery may be used to help patients eat and relieve symptoms caused by the cancer. This is called supportive or palliative surgery. Potential interventions of this type include:

  • Insert a percutaneous gastrostomy or jejunostomy (also called a feeding tube), so that a person can receive nutrition directly into the stomach or intestine. This may be done before chemotherapy and radiation therapy is given, to make sure that the patient can eat enough food to maintain his or her weight and strength during treatment.
  • Insert a special stent into the pylorus (the final part of the stomach that turns to intestine and is thus easy to be obstructed).

 

Chemotherapy

Chemotherapy is an important part of the treatment of a patient with gastric cancer, either as complementary treatment after surgical resection of the primary tumor (called adjuvant therapy), or as the only treatment modality in cases where an operation would not remove the tumor. A chemotherapy regimen (schedule) usually consists of a specific number of cycles given over a set period of time. A patient may receive one drug at a time or combinations of different drugs at the same time.

Chemotherapy can be given by mouth (orally) or injection. The goal of chemotherapy can be to destroy cancer remaining after surgery, slow the tumor’s growth, or reduce cancer-related symptoms. It also may be combined with radiation therapy. Currently, there is no single standard chemotherapy treatment regimen that is used worldwide. However, most chemotherapy treatments are based on the combination of at least two drugs, fluorouracil (5-FU), and cisplatin. Newer drugs similar to 5-FU, such as capecitabine, which is administered orally, and similar to cisplatin, such as oxaliplatin, appear to work equally well. Other drugs commonly used include docetaxel, paclitaxel, irinotecan, and epirubicin. In addition, it was recently found that patients whose stomach tumors have too much of the protein HER2 (called HER2-positive cancer) may benefit from adding trastuzumab to chemotherapy if they have advanced stomach cancer.

The side effects of chemotherapy depend on the individual and the dose used, but they can include fatigue, risk of infection, nausea and vomiting, hair loss, loss of appetite, and diarrhea. These side effects usually go away once treatment is finished.

 

Radiation therapy

Radiation therapy is the use of high-energy X-rays or other particles to kill cancer cells. A doctor who specializes in giving radiation therapy to treat cancer is called a radiation oncologist.

A radiation therapy regimen (schedule) usually consists of a specific number of treatments given over a set period of time. Patients with stomach cancer usually receive external-beam radiation therapy, which is radiation given from a machine outside the body.

Radiation therapy may be used before surgery to shrink the size of the tumor or after surgery to destroy any remaining cancer cells. It can also be used with a palliative purpose to relieve symptoms owing to obstruction or compression.

Side effects from radiation therapy include fatigue, mild skin reactions, upset stomach, and loose bowel movements. Most side effects go away soon after treatment is finished.

 

Metastatic stomach cancer

If cancer has spread to another location in the body, it is called metastatic cancer (stage 4). The survival expectation in these cases may be less than a year or even some months, but this may vary according to the kind of metastases and the biological behavior of the tumor. The only useful treatment strategy in these cases in chemotherapy, that has been shown to prolong the time interval until progression of the cancer to the body, and palliative radiotherapy, which may be used to alleviate symptoms of obstruction or compression.

For many patients, a diagnosis of metastatic cancer can be very stressful and, at times, difficult to bear. Patients and their families are encouraged to talk about the way they are feeling with doctors, nurses, social workers, or other members of the health care team.

 

Content on this site is not a substitute for professional medical advice. You should always consult your doctor.