The remarkable efficacy of imatinib in treating metastatic GISTs has prompted interest in developing an adjuvant after complete resection of GISTs. Resent phase III randomized trial involved 778 patients with localized GISTs who underwent complete surgical resection followed by 1 year of imatinib (400 mg/day) and revealed that adjuvant Inhibitors,research,lifescience,medical imatinib E7080 significantly improved the 1-year RFS rate (98%) compared with the placebo (83%) (P<0.0001) (156). Based on the results of this trial,
FDA approved imatinib as adjuvant therapy for GISTs (157). The most recent management guidelines in US (NCCN) (138) and Europe (ESMO) (139) recommended adjuvant imatinib for at least 1 year following complete surgical resection in patients with intermediate- to high-risk GIST. However, the optimal duration of adjuvant therapy has not been established yet. Treatment of localized unresectable or metastatic gists Although surgical intervention was applied to patients with metastases prior to the imatinib era, it was unlikely to completely resect the Inhibitors,research,lifescience,medical tumor and consequently with earlier recurrence than localized disease (45). Nunoby and colleagues (158) in Japan studied Inhibitors,research,lifescience,medical the outcome of
surgical resection in 18 patients with liver metastases of GISTs and showed 83% complete resection of liver metastases with 64% 3-year postoperative overall survival (OS) rate and 34% 5-year postoperative OS rate. However, the recurrence rate in the remnant liver Inhibitors,research,lifescience,medical and in other organs reached 94% in this study. Surgical treatment alone for metastatic GISTs, therefore, is only palliative (158). The application of imatinib for patients with advanced and non-resectable GISTs was first evaluated in the palliative setting in 2000 (24). A recent large clinical study of imatinib for unresectable or metastatic GISTs revealed up to 57 months of median OS
rate (159), which is almost a threefold increase in OS from about Inhibitors,research,lifescience,medical 20 months (45) prior to the application of imatinib. Based on the clinical practice guidelines (NCCN & ESMO), treatment with imatinib (400 mg/day) now is the standard of care for patients with locally advanced, recurrent, or metastatic disease (138,139). Multiple phase III clinical trials have confirmed the effectiveness of imatinib with standard-dose (400 mg/day) or high-dose (800 mg/day) (159,160). Furthermore, the efficacy of imatinib much certainly also depends on the mutant profile of GISTs. KIT exon 11 mutations show the greatest benefit from imatinib treatment (400 mg/day) (Figure 1) (135,161). KIT exon 11 codon 557/558 deletion/insertion mutations have a more aggressive clinical behavior (162). KIT exon 9 mutant GIST requires a higher imatinib dosage to reach a better response (135,163). In addition, sunitinib, another TKI, is beneficial for exon 9 mutated-GIST (30).