Gastrointestinal Stromal Tumor (GIST)

Introduction:

GIST (gastrointestinal stromal tumor) is a type of tumor that starts in the digestive system. GIST most commonly occurs in the small intestine and stomach. Gastrointestinal stromal tumors (GISTs) happen when specific cells called the interstitial cells of Cajal lining the digestive tract grow and divide in an uncontrolled way, creating a mass of tissue.  GISTs are rarely cancerous. People suffering from GIST may not notice any changes in their health, while others may feel unwell or have pain or bleeding.

Gastrointestinal stromal tumors (GISTs) are rare tumors. GISTs can start anywhere in the digestive (gastrointestinal) tract, from the oesophagus to the anus. 

Signs and symptoms:

Some people do not notice any signs of gastrointestinal stromal tumors (GISTs). Alternatively, their tumors are discovered by chance through diagnostics or surgical intervention for another reason. Others may experience symptoms like:

• Decreased appetite
• Tiredness
• Stomach pain
• Weight loss
• Vomiting blood
• Blood on or in the stool or black stools
• Bowel obstruction
• Difficulty swallowing

Staging:

TNM classification of gastrointestinal stromal tumours

TX-Primary tumour cannot be assessed

T0-No evidence of primary tumour

T1-Tumor ≤ 2 cm

T2-tumor greater than 2 cm but less than 5 cm

T3-Tumor > 5 cm but ≤ 10 cm

T4-Tumor > 10 cm in greatest dimension

Regional lymph nodes (N)

N0-No regional lymph node metastasis

N1-Regional lymph node metastasis

Distant metastasis (M)

M0-No distant metastasis

M1-Distant metastasis

Diagnosis:

There are various imaging techniques and laboratory tests a doctor may suggest if he suspects GISTS.

• Imaging tests. Imaging tests help the healthcare team to find the tumor and determine the site and size. Tests might include ultrasound, CT scan, positron emission tomography (PET) CT, and MRI scans .
  1. Upper GI endoscopy: This test may be done to locate the tumour and/or obtain a piece of the tumour (biopsy). In endoscopy, the doctor places a tube with a camera at the end into the mouth, through the oesophagus, and into the stomach. This allows the doctor to look at the tumour.
  2. Endoscopic ultrasound (EUS). This test also employs an endoscope, but this time an ultrasound probe is attached to the edge of the scope. The ultrasonographic sensor utilizes sound waves to produce images of the malignancy and determine its size.
  3. Computed tomography (CT): A scan of the abdomen and pelvis may also be obtained to help the doctor understand the location and size of the tumour. CT will also help to decide if the tumour can be surgically removed.
  4. Positron emission tomography (PET): A PET scan may also be performed to ensure the tumour is truly localized (in one place) and can be surgically removed. If your surgeon can take out the tumour as a whole then the surgery will be performed. After removal, the pathologist will study the tumour under a microscope to find out if it is a GIST. They’ll also be able to test the tumour for genetic changes. When the tumour is large or has metastasised and cannot be surgically removed then in this case, a biopsy is performed.
• Biopsy: A small sample of the affected tissue is extracted to analyse under the microscope in the laboratory.
  1. Biopsy by fine-needle aspiration. This technique extracts a tiny sample of tumour tissue to be examined in a lab. This test is similar to EUS, but with a thin, hollow needle on the endoscope's tip. The tumour is discovered with an EUS. The needle is used to collect tiny quantities of tissue for laboratory testing.

Often the needle is unable to collect sufficient cells, or the outcomes are unclear. Surgery may be required to obtain the sample.

• Laboratory tests on biopsies. A biopsy sample from your tumour is sent to a lab for analysis. Specialists examine the cells in the lab to determine whether they are cancer cells. Other tests offer your provider with information about your cancer cells, which is essential to plan your therapy.

GIST care and management are better achieved by a collaborative team of experts. Each expert must weigh the advantages and disadvantages of each treatment option.

Treatment:

The type of treatment the doctor recommends will depend on the size and location of the GIST, the results of lab tests, and the stage of the tumor.  The doctor usually considers the patient's age and general health before planning and performing surgery. Treatment options for GIST involve surgical intervention and/ or aimed drug therapy. 

Four types of standard treatment are used:

• Surgery: Resectable tumors or tumours that have been shrunk after drug or radiation therapy can be cured by surgical procedures.
• Targeted drug therapy: Some tumours are too huge or have disseminated to other parts of the body, making surgery ineffective. Imatinib, a targeted medication treatment, may be recommended in certain cases. In roughly 85% of patients, this drug can decrease or stop the tumour from developing. If your tumour cells develop resistance to imatinib, other targeted medications may be effective in shrinking the GIST. Sunitinib, regorafenib, and ripretinib are examples.
• Watchful waiting: Your physician will most likely keep you on track to Computed tomography every between three and six months. PET scans are occasionally sometimes used evaluate your response to therapy.
• Supportive care

Conclusion:

GISTs are uncommon tumours that can arise any place in the gastrointestinal tract. Some GISTs can cause bleeding, abdominal pain, and bloating. Other GISTs do not exhibit any side affects and are realised by chance throughout a methodology for another illness. Some GISTs are cancerous, but with treatment, the prognosis is favourable. It is essential to monitor your body and inform your physician if anything unusual occurs.