Gastric Gastrointestinal Stromal Tumors Treatment & Management
- Author: Michael A Choti, MD, MBA, FACS; Chief Editor: N Joseph Espat, MD, MS, FACS more...
Although surgical resection is the treatment of choice for gastrointestinal stromal tumors (GISTs) and offers the only chance for cure, the tyrosine kinase inhibitor imatinib mesylate (Gleevec) plays a major role.[10, 17, 25, 26] The uses of imatinib include the following :
Treatment of GISTS that are unresectable, metastatic, or both
Preoperative treatment of GISTs that are resectable with negative margins but with risk of significant morbidity
Adjuvant treatment following complete gross resection of GIST, to reduce recurrence
Imatinib shows the highest activity in GISTs that contain the mutation in exon 11 of c-KIT; approximately 90% of those patients respond. Of patients with GISTs that contain a KIT exon 9 mutation, approximately 50% respond; response improves when imatinib is given in a dose of 800 mg rather than the standard dose of 400 mg. Most GISTs with PDGFRA gene mutations respond, with the notable exception of those with D842V.
Imatinib comes in 100-mg tablets and can thus be given in graduated doses (100, 200, 300, 400, 500, 600, 700, 800 mg) while monitoring treatment responses. The adverse reactions of imatinib are manageable and include edema, rash, diarrhea, nausea, abdominal pain, and fatigue. Treatment interruption or dose reduction may be necessary in patients who develop severe hepatotoxicity or other severe adverse reactions.
In patients who have had their dose reduced due to severe toxicities, responses have been observed with a dose as low as 100 mg. Importantly, clinical trials have determined the efficacy of commonly prescribed doses (400, 600, and 800 mg). In general, doses below 300 mg should be avoided. The maximum tolerated dose of imatinib is 800 mg/d.
The standard dose of imatinib is 400 mg by mouth daily. The prescribed dose should be taken with a low-fat meal and a large glass of water. Doses of 400 mg or 600 mg should be administered once daily, whereas a dose of 800 mg should be administered as 400 mg twice a day.
In patients who received imatinib preoperatively and whose GIST was completely resected, the National Comprehensive Cancer Network recommends considering continuation of imatinib postoperatively. Although the duration of imatinib use in this setting has not been studied in randomized trials, data support continuation for 2 years postoperatively.
The use of imatinib as adjuvant therapy to prevent recurrence of primary GIST was approved by the US Food and Drug Administration (FDA) in 2008.[10, 28] In January 2012, the FDA extended the approved duration of use from 1 year to 3 years following surgical removal of CD117-positive GISTs. The approval was based on a randomized study in 400 patients with KIT (CD117)–positive GISTs, which found that at the median 5-year follow-up, overall survival was greater in patients treated for 3 years than in those treated for 1 year (92% vs 82%; hazard ratio [HR], 0.45; P = 0.019); 5-year relapse-free survival was also significantly superior (65.6% vs 47.9%; HR, 0.46; P < 0.0001).
In the setting of metastatic/advanced GIST, the NCCN recommends continuous use of imatinib until clear evidence of progression occcurs. For progressive disease, the imatinib dosage may be increased to 800 mg daily for patients with acceptable performance status (Eastern Cooper ative Oncology Group [ECOG] score 0-2), or therapy may be switched to sunitinib (Sutent), a newer tyrosine-kinase inhibitor that has been shown to provide significant clinical benefit in imatinib-resistant advanced GIST.
The FDA approved sunitinib in 2006 for the treatment of patients with GISTs whose disease has progressed or who are unable to tolerate treatment with imatinib. An interim analysis showed that sunitinib treatment delayed the median time to tumor progression of GISTs to 27 weeks, as compared with 6 weeks for patients who did not receive the drug.
The tyrosine kinase inhibitor regorafenib (Stivarga) was approved in February 2013 for locally advanced, unresectable GISTs that no longer respond to imatinib or sunitinib. The pivotal phase III trial showed that regorafenib plus best supportive care (BSC) significantly improved progression-free survival (PFS) compared with placebo plus BSC. Median PFS was 4.8 months for regorafenib and 0.9 months for placebo.
In a meta-analysis of three randomized, controlled studies in GIST patients with imatinib resistance or intolerance who received treatment with sunitinib, nilotinib, or regorafenib (n = 541) or placebo/supportive care (n = 267), progression-free survival, but not overall survival, significantly improved in the tyrosine kinase inhibitor treatment group. In patients with resistance or intolerance to both imatinib and sunitinib, treatment with nilotinib or regorafenib improved progression-free, but not overall survival.
Despite the proven success of imatinib and other newer tyrosine kinase inhibitors, surgical resection remains the treatment of choice and offers the only chance for cure from GIST.[33, 34, 35, 36, 37, 38] The main operative principle is resection of the tumor with negative microscopic margins. Wide resection of the tumor (eg, 2-cm margin) has not been shown to improve outcomes and expert consensus is that such dogmatic adherence to a particular width of margin is not necessary or recommended.
For small gastric tumors, wedge resection is adequate, if technically possible. Larger tumors necessitate subtotal or total gastrectomy. Enucleation should be avoided because predicting malignant potential preoperatively is difficult, even in benign-appearing lesions.
For locally invasive tumors, en bloc resection of adjacent involved organs, such as colon, spleen, or liver, may be indicated. Routine lymphadenectomy is not indicated, as lymph node involvement is very rare.
Recurrence and survival are not associated with the type of resection (wedge resection versus any type of gastrectomy) provided that a complete resection (R0) is performed.
Direct every effort at avoiding tumor rupture during the operation. Tumor rupture is associated with a worse prognosis because of peritoneal seeding.
In cases of disseminated disease, consider palliative resection because long-term survival has been reported in certain cases. Also consider resection in patients with recurrent disease that manifests as a solitary lesion in the liver or peritoneal cavity. Published reports of liver resection for hepatic metastasis from gastric and other GISTs suggest a survival benefit in selected patients.
Given the ability of imatinib to render initially inoperable GIST tumors resectable, there may be a role for cytoreductive surgery (R0 or R1 resection) in the setting of recurrent metastatic disease confined to the abdomen. Patients should have been on at least 6 months of therapy with imatinib or another tyrosine kinase inhibitor and have had either stable or partially responsive disease during this period.
A significant minority of these patients require liver resections (40%) and the majority require multivisceral resection, including bowel resections, peritonectomy, and/or omentectomy (60%). Even after such aggressive resection, R1 resections (microscopically positive resections) are the rule, R0 resections are rare, and about 5% of patients still have bulky disease remaining.
Up to 70% of patients able to undergo an R0/R1 resection in the setting of stable or partially responsive disease enjoy a progression-free survival as long as 4 years after the initiation of imatinib therapy.
Because adequate resection for small malignant GISTs can be achieved by wedge resection, minimally invasive surgery techniques can be considered in selected cases. Numerous published reports of laparoscopic resection of gastric GISTs have demonstrated the feasibility and safety of this technique.[43, 44, 45, 46, 47, 48, 49]
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|Group||Tumor Size||Regional Lymph Node||Metastasis||Mitosis|
|Stage IA||T1 or T2||N0||M0||Low|
|Any T||N1||M0||Any rate|
|Stage IV||Any T||Any N||M1||Any rate|
|Mitoses per 20 HPF||5-Year Survival Rate|
|< 6||< 4||97.5%|