Gastrointestinal stromal tumor

Disease Description (Causes and Symptoms)

• Definition and pathophysiology: Gastrointestinal stromal tumor (GIST) is a tumor originating from the smooth muscle lineage or interstitial cells of Cajal (ICC) in the wall of the gastrointestinal tract, and is mainly caused by mutations in the c-KIT (or PDGFRA) gene. The tumor forms a relatively well-demarcated nodule in the submucosal or muscular layer. Tumor size and the mitotic index determine the degree of malignancy and risk of recurrence.
• Main symptoms: Often asymptomatic in the early stages. When symptoms occur, they may include abdominal pain, bloody stool or hematemesis (bleeding), nausea and vomiting, an abdominal lump (palpable mass), constipation (when occurring in the colon), weight loss, fatigue and anemia, and, rarely, peritonitis (in the event of perforation) and fever.
• Epidemiology and prognosis overview (summary): Occurs in the stomach (approximately 50%), small intestine (approximately 25%), and large intestine (approximately 5–10%), in that order. When the tumor develops in the small or large intestine, it tends to be more malignant than when it develops in the stomach. Lymph node metastasis is rare, and hematogenous metastases occur mainly in the liver and lungs. The prognosis is favorable when complete resection is possible; the 5-year survival rate has been reported as approximately 50–65% in the literature. The recurrence rate varies according to the stage and presence or absence of residual lesions (recurrence is possible in some cases of localized disease).

Treatment Methods

• Standard treatment
  • Complete surgical resection (R0 resection of the lesion): If there is no metastasis, curative resection is the principle. Extensive lymph node dissection is usually unnecessary because lymph node metastasis is rare.
  • Endoscopic and laparoscopic surgery: Depending on the tumor size and location, options include endoscopic mucosal resection, laparoscopic wedge resection (a safety margin of approximately 2 cm is recommended), and partial resection.
  • Drug therapy (molecularly targeted therapy)
    • First-line: Imatinib (Gleevec) — standard treatment for unresectable or metastatic disease and as adjuvant therapy (when the risk of recurrence is high). It has treatment response and tumor-shrinking effects.
    • Second-line and subsequent treatment: In cases of imatinib resistance, sunitinib, regorafenib, and other drugs may be used (considering the genetic mutation and pattern of resistance).
  • Adjuvant and neoadjuvant therapy: For large tumors or when reducing the extent of resection is necessary, preoperative neoadjuvant therapy with imatinib may be attempted to shrink the tumor. In patients at high risk of recurrence, postoperative adjuvant therapy may be recommended for a certain period (the duration is determined according to the genotype and risk level).
• Testing and monitoring
  • Tissue biopsy (immunohistochemical markers: CD117 (c-KIT), DOG1, etc.) and genetic mutation testing (including PDGFRA) assist in evaluating treatment response and selecting medications.
  • Computed tomography (CT) is used to determine the stage, identify distant metastases, and perform follow-up examinations after treatment.
  • Endoscopic ultrasound (EUS) is used to assess the layer of origin and size of the tumor and to perform needle biopsy.
  • Blood tests (anemia, liver function, etc.) and, when necessary, establishment of an interval for imaging follow-up.
• Precautions, risk of complications, and self-care
  • Bleeding (gastrointestinal bleeding), intestinal obstruction, and intestinal perforation may occur — emergency evaluation is necessary if these symptoms occur (severe abdominal pain, persistent vomiting, or sudden bleeding or worsening anemia).
  • Medication side effects: Imatinib and other drugs may cause skin rash, gastrointestinal symptoms (nausea, vomiting, and diarrhea), edema, abnormal liver function, and hematologic abnormalities. Rarely, rapid tumor shrinkage may cause bleeding or perforation.
  • After surgery: General surgical complications such as infection, fistula, and changes in organ function.
  • Lifestyle management: Smoking cessation and limiting alcohol are recommended. Maintain a balanced diet (standard nutritional intake), and monitor for symptoms of bleeding and anemia in daily life (dizziness, chest discomfort, black stools, etc.).
  • Lesion follow-up: Small, low-risk lesions (e.g., ≤2 cm) do not necessarily require surgery, but regular imaging and endoscopic follow-up are necessary.

Checklist Before an Outpatient Visit (Including Sample Questions)

• Items to prepare (bring with you)
  • A list of currently used medications (including prescription drugs, over-the-counter medications, and supplements)
  • Copies of previous medical certificates, surgical records, pathology results, and imaging (CT, endoscopy, EUS, etc.)
  • Recent blood test results, if available, and information about allergies and underlying medical conditions
  • A record of symptom changes (when they began, progression, bleeding, pain, vomiting, weight changes, etc.)
• Examples of items to confirm during the outpatient visit (the consultation can be more efficient if the patient records these in advance)
  • Bleeding symptoms (bloody stool, black stool, vomiting blood), and the location, intensity, and frequency of abdominal pain
  • Changes in weight, appetite, and bowel movements
  • Medications recently taken (including anticoagulants and antiplatelet drugs)
• Documents and images to bring to the outpatient visit: Previous pathology reports (including immunohistochemical marker and mutation test results) and imaging files or reports

General Examples of Questions to Ask the Doctor

• "What are the size of my tumor and its mitotic index, and how is the associated risk level (low, intermediate, or high) classified?"
• "Is surgery necessary? If surgery is performed, what extent of resection is expected (partial resection versus curative resection)?"
• "If imatinib treatment is necessary, how long will I need to take it, and what are the common side effects? How should side effects be managed if they occur?"
• "What is my risk of recurrence, and how often should follow-up tests (imaging and endoscopy) be performed?"
• "Are there any particular lifestyle factors I should pay attention to (diet, exercise, or medications)?"

Examples of Disease-Specific Questions

• "What were the results of the c-KIT or PDGFRA mutation tests in my pathology report, and how do these results affect medication selection (for example, responsiveness to imatinib)?"
• "If my tumor is currently unresectable or metastatic, could neoadjuvant therapy or systemic therapy increase the possibility of surgery (resectability)? What are the expected treatment duration and goals?"