As in many rare cancers, having GIST often comes with far more questions than answers. The good news is that there has been a great deal learned about this cancer in the years since its relatively recent discovery. Below we address some of the most common questions we receive from patients and loved ones regarding GIST. If you have questions that aren’t answered here we encourage you to contact us at firstname.lastname@example.org or sign up for Life Raft membership to join GIST Chat where patients, staff and experts exchange advice, news and support.
What type of cancer is Gastrointestinal Stromal Tumor (GIST)?
Gastrointestinal stromal tumor (GIST) is a subtype of soft tissue sarcoma. It is a malignancy of mesenchymal origin arising from the gastrointestinal tract (GI). Mesenchymal tissues are part of many organs that help give the organ shape and strength. Most GISTs originate in the stomach, but can also be found in the small intestine, colon, rectum and esophagus.
How are GISTs formed?
“Cancer” is a term for a large number of diseases characterized by uncontrolled cell division and metastasis (the spread of cancer cells to different parts of the body). Cancer is created when normal cells acquire genetic mutations which trigger unhealthy levels of cell growth and division.
In the case of GIST, it is the interstitial cells of Cajal (the cells in the wall of the GI tract that signal muscles to move food along the tract) that divide uncontrollably when mutated, eventually forming a GIST. The cause of this mutation is KIT, a protein produced in abundance and relied upon by the interstitial cells of Cajal for development and maintenance.
To date evidence does not suggest that environmental factors or lifestyle choices play a role in a person developing GIST.
Where in the body is GIST found?
As the name suggests, GIST can occur anywhere in the GI tract. About 40-70% of GISTs are found in the stomach, 20-40% in the small intestine, 5-15% in the colon and rectum and in rare cases, the esophagus (<5%). On occasion, GISTs can also develop outside the GI tract. These are called eGISTs.
GIST often spreads from the original (primary) site to distant locations. If this happens, these tumors are called metastases (or simply, “mets”). If GIST tumors metastasize they usually travel to the liver, or the peritoneum. Metastases to the lymph nodes and lungs are rare, but do occur.
When GIST spreads to the liver, the liver tumors are GIST tumors, not liver cancer. GIST metastases in the liver are still derived from GIST cells and must be treated like GIST cells. Liver cancer is a completely different cancer that starts in the liver.
How common is GIST?
Although the exact incidence is still somewhat unclear, it is now estimated that, in the United States, an estimated 3,000 to 6,000 cases of GIST are diagnosed annually. Studies now are evaluating the global incidence of GIST and these estimates range anywhere from 6.6 to 14.7 cases per million.
The majority of GIST cases occur spontaneously in people over age 50. However, there is a rarer sub-set of the cancer termed SDH-deficient GIST that disproportionately affects children and young adults. Other potential risk factors include having neurofibromatosis (a condition that affects neural cells) and/or a family history of GIST syndrome, a rare, inherited form of GIST.
Are there early warning signs of GIST I should be on the lookout for?
In the stages of early tumor growth there are rarely any symptoms experienced. Symptoms that do appear are indistinct and often mistaken for other conditions such as IBS or anemia. This can make diagnosis a slow and difficult process, further illustrating the need for GIST awareness and education—especially in the medical community.
What are symptoms of GIST?
- Vague abdominal pain
- Early feeling of fullness (satiety)
- Abdominal bleeding (blood in stool or vomit)
- Fatigue due to anemia (low blood counts)
How is GIST diagnosed?
GIST is often discovered in the course of routine testing including:
- Upper endoscopy (inspection of organs or cavities using a device called endoscope)
- Laparoscopy (abdominal exploration using a device called a laparoscope)
- Ultrasound (using sound waves to take images of internal organs)
- Computed tomography (CT or CAT) scan (a radiographic technique that produces a film that represents a detailed cross section of tissue structure)
- Magnetic resonance imaging (MRI) (another medical imaging technique)
After a mass is found, even if it is suspected to be GIST, a biopsy is needed to provide a confirmed diagnosis. Although there are various methods for performing biopsies based on a patient’s needs, their basic function is to extract cells from the abnormal area. These cells are then sent to a pathologist for further histologic testing.
Once diagnosed with GIST, do I need to see a specialist? What type?
It is our opinion that nothing can take the place of a physician who has a lot of experience in treating GIST. This may include a Pathologist, Oncologist, and/or Surgeon. GIST is such a rare cancer that few community doctors have much experience in treating it. Larger hospitals with top sarcoma treatment centers are likely to have more experience with GIST. This is especially true of hospitals which regularly conduct clinical trials. GIST specialists are oncologists who treat many GIST patients and as such are well versed in their unique needs, keep current on the newest treatment options, can help to manage side effects, provide proper monitoring, and are knowledgeable about alternatives if the initial treatment fails.
The Life Raft Group has compiled a list of GIST specialists sortable by name, location and specialty that you may find useful when searching for the closest GIST specialist to you.
How is GIST treated?
If a patient has operable disease the physician or oncologist will likely recommend surgery to remove the tumor/s. The decision to operate will depend on the difficulty of the surgery, whether the disease has metastasized, size of the primary tumor and the general health of the patient.
Additionally, there are currently three FDA-approved oral chemotherapies for the treatment of GIST (imatinib, sunitinib, regorafenib). These are prescribed based on GIST mutational status, risk factors and what stage of disease progression the patient is currently in.
How long should I expect to be on imatinib (Gleevec)?
There are differences in opinion regarding the duration of imatinib (Gleevec) therapy. For example, the US FDA recommends three years but also said that optimal length of treatment is not known. Based on the NCCN guidelines, at least 36 months should be considered for HIGH RISK tumors.
These guidelines still leave a lot of questions unanswered including whether tumors will recur after stopping adjuvant (taken after the initial treatment for GIST, usually surgery) imatinib, and if they do whether they will then be resistant to imatinib. This leads to the larger overall question of whether treatment should be taken in hopes of preventing GIST tumor recurrence or wait to be taken until visible disease is found.
These are large questions that are variable based on the individual and cannot be answered with full certainty as the future course of everyone’s disease is unknown to a certain degree. Please note that the opinions expressed herein are not made by doctors and we strongly urge you to work in combination with yours when making any treatment decisions.
Imatinib can kill GIST tumor cells, but is seldom able to kill 100% of GIST tumor cells. In some patients, it may kill some cells, but merely keep others from growing. This is why metastatic/advanced patients are advised to take imatinib for life.
In the case of preventive imatinib (taken after complete resection of primary tumor), it is possible for microscopic tumors to remain. Again, while imatinib may kill almost all of these cells, it may not kill them all. This may be why many patients see more benefit from three years of preventive imatinib than just one, as well as why some GIST experts recommend imatinib for life in patients with a high risk of recurrence.
In adjuvant imatinib clinical trials such as the Z9001 trial (1 year vs placebo) and the Scandinavian trial (one year vs three years) it has been shown that GIST often returns 6 to 12 months after stopping treatment. You can read more about these here.
While it is advisable for high-risk GIST patients whose mutation is imatinib -responsive to be on the drug longer than three years if they are tolerating it well, not all GISTs are high-risk. Surgery cures many, if not most, low-risk GISTs. Treatment for intermediate risk GISTs are more open to personal preference. Some of these patients prefer adjuvant imatinib, while some might not. Whether or not a patient has a responsive mutation type, patient preference and how well imatinib is tolerated (once started) are all very important factors to consider in this decision.
Are there differences between types of imatinib (Gleevec)?
In Feburary of 2016, Novartis Pharmaceuticals lost its exclusive patent on imatinib production in the United States and the first generic (in the United States) version of imatinib entered the market. Manufactured by Sun Pharmaceuticals, it is currently only indicated for use in CML patients. This is because only the portion of the patent for the CML indication of imatinib (Gleevec) has expired. The portion of Novartis’ patent linking imatinib as a treatment for GIST remains exclusive until 2020. Since this part of the patent has not yet expired, Sun Pharmaceuticals cannot legally say at this time that their product is indicated for GIST. However, this is not to say that the drug will not work for GIST patients, since the generic drug contains the same active ingredient as the innovator drug.
As the first to file for generic marketing in the US, Sun Pharmaceuticals was given a six-month market exclusivity, which expired in August 2016. Upon that expiration, two other imatinib generic manufacturers – Apotex and Teva, have been given market approval by the FDA. Moving forward, more manufacturers will gain approval and increase the production of generic imatinib.
Due to a myriad of legal restrictions, GIST patients may find disconnects between the version of the drug the doctor prescribes, what the pharmacy fills, what their insurance covers and what Sun Pharmaceuticals will provide support for.
To address the numerous concerns of patients regarding the introduction of generics into the marketplace, the Life Raft Group has set up a generics resource center on its website to continue reporting on these issues and provide support and information to help patients navigate this expanded treatment landscape.
What sorts of side effects should I expect from my oral chemotherapy?
Oral chemotherapy is much like traditional chemotherapy in that side effects are incredibly variable among patients. Although there are commonly experienced side effects among GIST patients, how an individual will tolerate a drug is very personal. For more information on side effects, see this link to Managing Side Effects.