Gastrointestinal Stromal Tumor - Therapy

Therapy

Tumor size, mitotic rate, and location can be used to predict the risk of recurrence in GIST patients. Tumors <2 cm with a mitotic rate of <5/50 HPF have been shown to have lower risk of recurrence than larger or more aggressive tumors. Nevertheless, all GIST tumors should be considered to have malignant potential and no GIST tumor can be correctly classified as "benign."

Surgery is the mainstay of therapy for nonmetastatic GISTs. Lymph node metastases are rare, and routine removal of lymph nodes is typically not necessary. Laparoscopic surgery, a minimally invasive abdominal surgery using telescopes and specialized instruments, has been shown to be effective for removal of these tumors without needing large incisions.The clinical issues of exact surgical indications for tumor size are controversial. The decision of appropriate laparoscopic surgery is affected by tumor size, location, and growth pattern.

Until recently, GISTs were notorious for being resistant to chemotherapy, with a success rate of <5%. Recently, the c-kit tyrosine kinase inhibitor imatinib (Glivec/Gleevec), a drug initially marketed for chronic myelogenous leukemia, was found to be useful in treating GISTs, leading to a 40-70% response rate in metastatic or inoperable cases.

The two year survival of patients with advanced disease has risen to 75–80% following imatinib treatment.

Data presented at the 2007 ASCO meeting showed adjuvant treatment with imatinib following surgical resection of GIST tumors can significantly reduce the risk of disease recurrence (6% recurrence on imatinib vs. 17% without therapy at 12 months). The optimal duration of adjuvant therapy is currently unknown; trials are ongoing evaluating treatment durations of 1, 2, and 3 years.

Patients who develop resistance to imatinib may respond to the multiple tyrosine kinase inhibitor sunitinib (marketed as Sutent).

The effectiveness of imatinib and sunitinib depend on the genotype.