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Gastrointestinal Stromal Tumor (GIST)

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Treatment

Surgical Care

Radical and complete surgical resection is the gold-standard treatment which offers individuals with gastrointestinal stromal tumors (GISTs) the best chance for complete remission. Complete remission is more likely if the GIST is smaller, more localized, and identified early. Surgery is also the treatment of choice in symptomatic individuals who have local spread or metastatic disease progression of GIST. Laparoscopic resection techniques for GIST have advanced, so this less invasive surgical option is more frequently contemplated and utilized. Often, surgical resection of large tumors is performed in conjunction with adjuvant or neoadjuvant therapy using imatinib mesylate.1 

The primary objective for surgical management of GIST is complete resection of the tumor with negative microscopic margins. There is no known benefit to performing wide resection of the tumor, so it is not recommended. Local resection for smaller GISTs may be effective. Small intestinal GISTs may require segmental resections, while gastric GISTs may require wedge resections.2 Surgical resection should also be considered for individuals with recurrent localized GIST as well as palliative resection for those with metastatic GIST due to potential long-term survival benefits. 

Surgical approaches may be performed via endoscopy, laparoscopy, or open incision. Endoscopic full-thickness resection (EFR) of smaller GISTs less than 5 cm in size has a lower resection rate (95.3%) compared to laparoscopic or open surgical resection (100%); however, there are decreased postoperative complications, shortened lengths of hospital stay, and decreased costs with the endoscopic approach to GIST resection.3 Laparoscopic removal of gastric and small intestinal GISTs less than 5 cm in size is a feasible and safe possibility, promoting shorter hospital stays, faster return to a normal diet, and less pain medication usage. Laparoscopic excision of GISTs larger than 5 cm yielded similar outcomes when compared with open resection surgeries in terms of in-hospital morbidity and 5-year recurrence-free survival rates.2 

For GIST tumors which have spread locally, the surgeon may perform an en bloc resection of adjacent involved organs such as the liver, spleen, or colon. Approximately 60% of GIST patients require multivisceral resection and about 40% specifically require liver resection. GIST spread to regional lymph nodes is rare, so lymphadenectomy is usually not indicated.2 

Tumor rupture and tumor enucleation are important occurrences to avoid during surgery to prevent metastasis of GIST to other regions in the abdominal peritoneum.2

Post-Operative Care

Vitals are monitored post-operatively as well as fluid intake and output. Patients are instructed to use a spirometer every 1 to 2 hours while awake post-operatively to prevent pneumonia. The head of the hospital bed may be elevated 30 to 45 degrees to prevent aspiration.2 

Postoperative prophylaxis against deep vein thrombosis and pulmonary embolisms is critical as these are primary causes of postoperative mortality. Prophylaxis includes sequentially graded compression stockings and administration of blood thinners.2 

Placement of a nasogastric (NG) tube is dependent on the type of resection performed. If used, it is left in place postoperatively. Removal of an NG tube depends on varying criteria determined by the operating surgeon. A urinary Foley catheter typically remains in place during the early postoperative phase. Foley catheters may be used preoperatively in patients who have experienced significant hemorrhaging or other complications due to GIST. Clinicians may remove the catheter once fluid shifting has stabilized. Anesthesia personnel may place an epidural catheter for postoperative pain control. Alternatively, they may devise a patient-controlled method of pain management.2 

Intravenous antibiotics are used to prevent infection of the surgical incision, as well as in cases of bowel perforation or postoperative septic complications.2  

Medical Care

Imatinib mesylate (Gleevec) is a first-line tyrosine kinase inhibitor (TKI) which is used to medically treat GIST. Imatinib may be used as an adjuvant therapy post-operatively for up to 3 years in patients who had high-risk tumors completely resected to prevent recurrence and improve survival rate. Imatinib may also be used as a neoadjuvant therapy to shrink existing large tumors that are considered marginally or borderline resectable prior to surgical excision. These GIST tumors may be located near blood vessels or other structures that would render the surgical procedure more dangerous, so shrinking them medicinally prior to the operation may be beneficial to decrease the chance of patient mortality or surgical complications.1 

When imatinib is not well tolerated by the patient or proves no longer effective against advanced GIST, treatment using other tyrosine kinase inhibitors is considered in a specific progression.1 Sunitinib (Sutent) is the second-line (TKI) for advanced GIST. Regorafenib (Stivarga) is the third-line TKI therapy for individuals who no longer respond to imatinib or sunitinib. Three fourth-line TKI agents have obtained FDA approval for treatment of advanced GIST, including avapritinib (Ayvakit), nilotinib (Tasigna), and ripretinib (Qinlock). There are a few fourth-line TKI agents under investigation, including sorafenib (Nexavar) and dasatinib (Sprycel). Pazopanib (Votrient) is a more general therapeutic agent with approval to target advanced soft tissue sarcomas.1

Consultations

Successful treatment and management of GIST involves a multidisciplinary team approach including a surgeon, oncologist, and gastroenterologist.4 The gastroenterologist performs the diagnostic testing necessary via endoscopy, capsule endoscopy, or colonoscopy in addition to other imaging studies to confirm the presence, size, and location of the tumor as well as potentially biopsy the GIST to ascertain malignancy. The surgeon handles all of the details regarding GIST resection, while the oncologist manages the tyrosine kinase inhibitor (TKI) drug interventions for adjuvant or neoadjuvant therapies in collaboration with the surgeon’s specifications and the information from the gastroenterologist’s imaging results. If the GIST is deemed marginally or borderline resectable, neoadjuvant drug therapy is required to shrink the tumor prior to surgical resection. Following complete GIST resection, the oncologist’s adjuvant TKI therapy is required to prevent recurrence of the GIST. TKI interventions stop or slow the progression of advanced GIST metastasis or regional spread which cannot be resected. Depending on the location and type of GIST, the surgeon may recommend different surgeries. If the primary tumor has not spread to other regions, the surgeon may recommend a partial gastrectomy, partial intestinal resection, abdominoperineal resection, or a pancreaticoduodenectomy (Whipple procedure).5 The surgeon manages pre-operative preparations as well as post-operative recovery. 

Diet

Following GIST resection, patients receive nutrition only via a nasogastric (NG) tube for varying durations of time according to surgeon preference. After removal of the NG tube, patients are started on a liquid diet and slowly advanced to a normal diet as tolerated. Registered dieticians may provide counsel regarding a postgastrectomy diet if patients underwent partial or total stomach removal. Specialized nutritional support may be required depending on the preoperative nutritional status of the patient. This may include total parenteral nutrition (TPN), peripheral hyperalimentation, or enteral tube feedings. Multivitamin and iron supplementation may be warranted, particularly in cases of GIST-induced gastrointestinal bleeding and anemia.6  

Long-Term Monitoring

It is important for patients who have had GIST resections to receive postoperative monitoring to check for recurrence that may require secondary or potentially multiple surgical interventions as well as to provide tyrosine kinase inhibitor therapy for unresectable or metastatic GISTs. Follow-up sessions include a physical examination, CT scanning, and at times periodic gastroscopies. Long-term management recommendations for patients classified with high-risk GIST include abdominal and/or pelvic CT scans every 3 to 6 months for 5 years, progressing to annual scans. Endoscopies every 6 to 12 months are used to monitor individuals without high-risk GIST categorization. For patients with metastatic GIST or persistent recurrence, follow-ups every 3 to 6 months are recommended. If patients obtain complete GIST resection, follow-ups should be every 3 to 6 months for 5 years to assess for complete GIST remission, progressing to annual follow-ups.7 

Prevention

The only identifiable risk factors for GIST development are age and rare, inherited genetic syndromes, both of which are unable to be prevented. Environmental and lifestyle-related factors are not known to trigger GIST development, so there are no conclusive methods of GIST prevention.8  

References

  1. Choti, MA. Gastrointestinal stromal tumors (GISTs): practice essentials, background, pathophysiology. Medscape. Published online April 3, 2021. Accessed June 22, 2021.
  2. Choti, MA. Gastrointestinal stromal tumors (GISTs) treatment and management: approach considerations, medical care, surgical care. Medscape. Published online April 3, 2021. Accessed June 22, 2021.
  3. Zhao Y, Pang T, Zhang B, et al. Retrospective comparison of endoscopic full-thickness versus laparoscopic or surgical resection of small (≤ 5 cm) gastric gastrointestinal stromal tumors. J Gastrointest Surg. 2020; 24(12):2714-2721. doi:10.1007/s11605-019-04493-6
  4. Choti, MA. Gastrointestinal stromal tumors (GISTs) treatment and management: consultations. Medscape. Published online April 3, 2021. Accessed June 22, 2021.
  5. Surgical removal of gastrointestinal stromal tumors (GIST). Penn Medicine – Abramson Cancer Center. Accessed June 27, 2021. 
  6. Choti, MA. Gastrointestinal stromal tumors (GISTs) treatment and management: diet. Medscape. Published online April 3, 2021. Accessed June 22, 2021.
  7. Choti, MA. Gastrointestinal stromal tumors (GISTs) treatment and management: long-term monitoring. Medscape. Published online April 3, 2021. Accessed June 22, 2021.
  8. Gastrointestinal stromal tumor causes, risk factors, and prevention.  Cancer.org. Accessed June 22, 2021. 

Article reviewed by Eleni Fitsiou, PhD, on July 1, 2021.

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