The diagnosis of GIST often starts with a physical exam and assessment of medical history. If GIST is suspected, severe tests may be required:
- Imaging tests: Ultrasound, computed tomography (CT), magnetic resonance imaging (MRI) and positron emission tomography (PET) scans provide images of the body to determine whether a suspicious spot may be a tumor, and the extent of its spread and assess effectivity of treatment.
- Upper endoscopy: known as esophagogastroduodenoscopy or EGD, an investigation consisting of a flexible thin tube connected to a tiny camera which will be inserted into a patient’s mouth, passing through the throat to evaluate the esophagus, stomach, and the first part of small intestine to evaluate for any abnormal sign.
- Endoscopic ultrasound (EUS): A tiny tube with camera is inserted into the throat down to the stomach and then a special ultrasound is utilized to view images of its internal structure. EUS can take photos of the tumor and calculates the size using sound waves.
- Fine-needle aspiration biopsy: Also known as an endoscopic ultrasound-guided fine needle aspiration (EUS-FNA), uses hollow needles to collect small amounts of tissue for lab testing. Rarely, the doctor might use an imaging test like a CT scan to guide the placement of a needle through the skin and into the tumor. In some cases, a surgery may be recommended if the results are unclear because the needle cannot reach enough cells.
- Laboratory tests on biopsies: A pathologist may be able to determine if a tumor is most likely a GIST after examining the tumor sample cells under a microscope. If they are potentially cancerous, the doctor may require more tests such as immunohistochemistry and molecular genetic testing for more information about the cells and for creating an effective treatment plan.
There are different types of treatments for GIST according to the size and location of the GIST, test results and overall health condition. Common treatments are targeted drug therapy and surgery.
In some cases, “watchful waiting” may be suggested. A patient’s condition is carefully monitored through scheduled appointments one or twice a year. No treatment is given until new or different indications or symptoms develop. This is common in very small tumors that are not growing quickly and is considered low risk.
Surgery as a treatment for GIST is often recommended on tumors that are localized or has not spread. The type of surgery is determined by the size and location of the tumor.
Small GISTs can be removed laparoscopically, a minimally invasive procedure that will require making a many small incisions in the abdomen to remove the tumor. The surgeon uses a laparoscope to visualize the internal organs. It is put into one of the small incisions that are created on the abdominal wall. This procedure allows shorter recovery time for patients.
For larger GISTs, especially if it affects neighboring organs, surgery may be not recommended right away. The initial course of treatment is to proceed with neoadjuvant therapy or targeted drug therapy to make the tumor shrink, making surgery to remove it easier.
Targeted drug therapy
Targeted drugs or precision medications are considered beneficial in treating GISTs. Certain proteins that aid in cell division and growth in gastrointestinal stromal tumor (GIST) cells can be targeted by these medications. These aim to block the tyrosine kinase enzyme, which promotes the growth of cancer cells, in GISTs. Compared to chemotherapy or radiation therapy, targeted therapies typically have a lower impact on healthy cells.
Imatinib, an oral pill, is often prescribed as the first course of targeted drug therapy for GIST, especially to:
- Reduce the risk of recurrence of cancer after surgery
- Reduce the size of the tumor for easier surgery
- Treat advance GISTs that has spread to other areas
- Manage recurring GISTs
Patients that became resistant to imatinib may be prescribed with other targeted drugs such as sunitinib, regorafenib and ripretinib. New medications are expected to become available in the future.
Although surgery or targeted drug therapy can remove or eliminate the GIST, there is still a chance that it may come back after the treatment. Doctors strongly suggest having a follow-up care to monitor the health condition and manage side effects of treatment, if there is any.