Overview
Gastrointestinal Stromal Tumours are a different kind of tumours, which arise from the wall of the digestive tract. These arise from the muscle layer of the lining of the gastrointestinal tract. They behave differently from the traditional cancers of the gastrointestinal system.
The most common sites of GIST include the stomach, although they have been reported in the food pipe ( oesophagus ), small intestine and even the large intestine.
Most GISTs have a genetic basis to their origin and certain changes ( mutations ) in the in genes for certain growth factors ( KIT ), result in an uncontrolled growth of these cells, resulting in the development of these tumours.
Presentation
- Bleeding: presents as vomiting with blood in vomiting or dark stools – Malena. Many times, patients simply present with anaemia -: low haemoglobin and further investigations lead to a diagnosis of GIST.
- Abdominal Pain.
- Loss of appetite and weight loss.
- Incidental ( by chance ) discovery on an ultrasound or CT scan done for any other reason.
Diagnosis
- Endoscopy: visualise the lesion and also a biopsy can be performed. Either an Upper GI or a colonoscopy will be required depending on the location of the lesion
- CT scan: identifies the lesion ( tumour ), and can also understand the size, extent and the relationship of the tumour to the surrounding structures – CT scan also helps plan the surgery.
Treatment
1. Surgery is the mainstay of the treatment – REMOVAL OF THE TUMOUR along with adequate margin is required.
The resected specimen is sent for analysis – histopathology and depending on certain histological features eg: size and extent of dividing cells ( mitoses ) – classification of the tumour is made and this defines if further treatment – an oral chemotherapy medication – imatinib is required or not
2. Chemotherapy – Imatinib ( Gleevec ) is a medication – which is an oral chemotherapy drug ( tablet ), which is specifically against GIST. The medication works best in individuals, who express the antibody CD117 ( Tyrosine Kinase Inhibitor positive: c KIT positive ).
This is used In 2 situations
Preoperative
This is to make the tumour smaller and make them amenable to surgery. initially, when the tumour is large and an operation cannot be done straight away, oral medication- Imatinib is used to make the tumour smaller. The medication is effective and works well.
Postoperative
In certain patients whose risk for recurrence is estimated based on
- Size of the tumour
- Presence of mitosis ( number of mitoses – dividing cells )