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.
Gastrointestinal stromal tumor (GIST) is considered to be a type of “soft tissue sarcoma”. However, the treatment of GIST and the prognosis for GIST patients is better than for most other soft tissue sarcomas. GIST is a malignancy of “mesenchymal” origin arising from the gastrointestinal tract (GI). Mesenchymal tissues are connective tissues that help to give organs their shape and strength. Most GISTs originate in the stomach, but they can occur anywhere along the GI tract, including the esophagus, small intestine, colon, and rectum.
“Cancer” is a term for a large number of diseases characterized by uncontrolled cell division and the potential for metastasis (spread of cancer cells to different parts of the body). Cancer arises when normal cells acquire mutations (genetic changes) which trigger uncontrolled cell growth and division.
GISTs arise from a particular (and otherwise obscure) group of cells, the “interstitial cells of Cajal” (pronounced KA-HAL; Cajal was the Spanish biologist who discovered this cell type), or “ICCs”. ICCs are “neuromuscular” cells, found in the wall of the GI tract, that signal muscles to contract rhythmically, moving food along the tract; these waves of contraction are called “peristalsis”.
Mutations in ICCs can lead to formation of a GIST. In most cases of GIST, the mutation occurs in a gene called “KIT”, a gene that encodes a protein expressed in (i.e., produced by) ICCs (and by very few other cell types).
There is no evidence that any environmental factors or lifestyle choices contribute to the risk of developing GIST – it seems to occur completely at random in the population. (The very rare cases of inherited GIST, discussed below, are exceptions.)
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%).
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.
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 per year.
The majority of GIST cases occur spontaneously in people over age 50. However, there is a rarer subset of the cancer, termed pediatric or “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.
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 ulcers, irritable bowel syndrome (IBS) or anemia. This can delay diagnosis, further illustrating the need for better GIST awareness and education—especially in the medical community.
GIST is often discovered in the course of routine testing including:
After a mass is found, even if it is suspected to be GIST, a biopsy is needed to confirm the 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.
We strongly advise finding a physician who has experience treating GIST. This doctor may be a Pathologist, Oncologist, or Surgeon. GIST is such a rare disease – perhaps only a single new case annually in a city of 200,000 – that some doctors and community hospitals may never have encountered it. Larger hospitals with specialized 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, helping patients to manage side effects, providing proper monitoring, and are knowledgeable about alternatives if the initial treatment fails.
You may find this GIST Specialist Directory useful when searching for the GIST specialist closest to you.
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. Some GISTs are cured by surgery alone – they never return. However, if the GIST has already metastasized, surgery alone cannot be curative, and drug treatment (chemotherapy) will usually be prescribed.
Additionally, there are currently three FDA-approved oral chemotherapies for the treatment of GIST (imatinib, sunitinib, and regorafenib). (Add avapritinib).These are prescribed based on GIST mutational status, risk factors and what stage of disease progression the patient is currently in.
There are differences in opinion regarding the duration of imatinib (Gleevec) adjuvant therapy. For example, the US FDA recommends three years but acknowledges that the optimal length of treatment is not known. Based on the NCCN guidelines, at least 36 months should be considered for HIGH RISK tumors.
Metastatic/advanced patients are advised to take imatinib for life, because even a single cell evading the drug could potentially give rise to a new tumor.
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 year, as well as why some GIST experts recommend imatinib for life in patients with a high risk of recurrence.
In February of 2016, Novartis Pharmaceuticals lost its exclusive patent protection on imatinib production in the United States and the first generic (in the United States) version of imatinib entered the market. 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. In spite of this, generic imatinib is widely prescribed or dispensed for GIST patients.
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 and what their insurance covers.
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.
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.