GIST belongs to the sarcomas — malignant tumors of connective tissue — but its malignant potential varies widely. Small tumors with a low mitotic count rarely come back after removal; large ones need additional treatment and long-term follow-up.

I have a small gastric GIST. Surgery or surveillance?

For a tumor under 2 cm without worrying features on endoscopic ultrasound, surveillance with regular checks is acceptable. If the tumor grows, changes, or surveillance worries you, it is removed — often laparoscopically, with a small operation.

Why test for mutations?

The mutation determines whether imatinib will work and at what dose. Some tumors are resistant to it — in that case targeted therapy before or after surgery is not given, or another drug is chosen.

How long should imatinib be taken after surgery?

For high risk of recurrence, the standard duration of adjuvant therapy is 3 years. For low risk after complete removal, it is not needed.

Can GIST be removed laparoscopically?

Yes, when the tumor’s location and the extent of resection allow and the tumor can be extracted without breaching the capsule. The final choice of approach is made after the work-up.

GIST of the stomach and bowel: surgery and imatinib therapy

A gastrointestinal stromal tumor (GIST) grows not from the lining, like cancer, but from cells deep within the wall of the stomach or bowel. That is why on endoscopy it is often seen only as a bulge under normal-looking mucosa, and a biopsy with standard forceps shows nothing. The main treatment is surgery: the tumor must be removed completely and gently, without breaching its capsule. For large tumors or tumors in difficult locations there is a targeted drug that may shrink the tumor before surgery and, at high risk of recurrence, lower that risk afterward.

Kateryna Valikhnovska, MD, surgical oncologist, during a laparoscopic operation — The laparoscopic stage of an operation: the lights in the operating room are dimmed because the surgeon works from the camera image on the monitor.

What GIST is and why it develops

GIST arises from cells that regulate contractions of the digestive tract wall. The tumor most often occurs in the stomach, less often in the small bowel, and rarely in the rectum and esophagus. Most tumors are caused by a mutation that arises within the tumor itself: in the KIT or PDGFRA gene. It is not inherited, but it determines whether targeted therapy will work. A small share of GISTs is linked to hereditary conditions — neurofibromatosis type 1 or SDH enzyme deficiency, more often in young patients.

The malignant potential of GIST varies: from tumors that almost never come back to those that spread to the liver and peritoneum. It is assessed by tumor size, the number of mitoses in the pathology specimen, location, and whether the tumor has ruptured.

Are there symptoms

Small GISTs cause no symptoms and are found by chance — on endoscopy, ultrasound or CT. Larger tumors may bleed, causing anemia, black stools or vomiting blood. Pain, a feeling of heaviness, a palpable mass in the abdomen, and, for tumors near the entrance to the stomach, difficulty swallowing are also possible.

Examinations needed

Contrast-enhanced CT of the abdomen and pelvis, plus chest CT — size, location, relationship to neighboring organs, liver and peritoneal metastases.
Upper endoscopy and endoscopic ultrasound — for tumors of the stomach, duodenum and rectum: which layer of the wall the tumor arises from and what features it has.
Endoscopic ultrasound-guided biopsy — when targeted therapy before surgery is planned or the diagnosis is unclear. If the tumor will be removed straight away anyway, a preoperative biopsy is not always needed.
Immunohistochemistry and molecular testing for KIT and PDGFRA mutations — mandatory: the mutation determines whether targeted therapy is needed and at what dose.
For rectal tumors — pelvic MRI.

When surgery is possible

Surgery is recommended when the tumor can be removed completely, with an intact capsule, and without mutilating the organ. For gastric tumors under 2 cm without worrying features on endoscopic ultrasound, surveillance is acceptable: they are removed if the tumor grows or changes, or if the patient chooses removal. Rectal lesions are recommended for biopsy or removal regardless of size.

If the tumor is large or located so that removing it would mean removing the whole stomach, part of the pancreas, or the rectum with the anus, targeted therapy with imatinib is given first — usually for 6–12 months, until maximal response, monitored by CT. After that it can often be removed with a smaller operation that preserves the organ.

If surgery is not possible now

With liver or peritoneal metastases, treatment is based on targeted therapy chosen according to the tumor’s mutation: imatinib first-line, and other drugs of this class on progression. For tumors with the PDGFRA D842V mutation, which are resistant to imatinib, there is a dedicated drug — avapritinib.

When metastases have responded well to targeted therapy and are few, the MDT may consider removing the residual tumor. The drug is continued.

How the operation is performed

The goal is to remove the tumor completely, with clear margins and an intact capsule: rupture during surgery sharply increases the risk of spread through the peritoneum. Wide resections are not needed: for gastric GIST, a section of the wall containing the tumor is usually removed — a wedge resection; for small bowel GIST, a segment of bowel. Non-enlarged lymph nodes are usually not removed, because GIST rarely spreads to them; enlarged nodes are removed, and for SDH-deficient tumors lymph node dissection is decided individually.

When the tumor’s location and the extent of resection allow, the operation is performed laparoscopically, through several small incisions. The tumor is extracted in a special retrieval bag so as not to damage it or spill cells.

With GIST, what matters is not the size of the operation but its precision: the tumor must be removed intact, without breaching the capsule.

Kateryna Valikhnovska, MD, surgical oncologist

Recovery after surgery

Care follows the enhanced recovery after surgery (ERAS) protocol: early mobilization, early feeding, controlled pain relief. After a gastric wedge resection or resection of a small bowel segment, digestion usually recovers, and a strict diet is mostly not needed afterward.

The risk of recurrence is assessed from the pathology results. For high risk, adjuvant imatinib for 3 years is recommended; for low risk it is not needed. If the tumor carries a mutation resistant to imatinib, adjuvant therapy is not given.

Follow-up

The CT schedule depends on the risk of recurrence: for high risk — every few months during adjuvant therapy and in the first years after it ends, then less often; for low risk — less often from the start. The doctor sets the intervals. New symptoms — pain, anemia, black stools — should be reported without waiting for the scheduled check.

What to bring to the consultation

CT discs and reports, upper endoscopy and endoscopic ultrasound results;
the pathology and immunohistochemistry report: tumor size, mitotic count, CD117, DOG1;
the result of molecular testing for KIT and PDGFRA mutations, if performed;
tissue blocks and slides — for review and molecular testing by another laboratory;
the operative report, if the tumor has already been removed, and details of imatinib treatment.

If some materials are missing, that is no reason to postpone the consultation: some examinations can be done on site.

The consultation is free of charge. How it goes and how long it takes is described on the page “Oncologist Consultation”.