***TASK*** the task is to summarize an input biomedical literature in six sentences 
    ***INPUT*** the input is a biomedical literature 
    ***OUTPUT*** the output is the summary of an input biomedical literature in six sentences 
    ***DOCUMENTATION*** 
    ***EXAMPLES*** 
    Input: UNLABELLED Gastrointestinal stromal tumors ( GISTs ) are gaining the interest of research ers because of impressive metabolic response to the targeted molecular therapeutic drug imatinib mesylate . Initial reports suggest an impressive role for (18)F-FDG PET in follow-up of therapy for these tumors . However , the role of (18)F-FDG PET versus that of CT has not been established . Therefore , we compared the roles of (18)F-FDG PET and CT in staging and evaluation of early response to imatinib mesylate  therapy in recurrent or metastatic GIST . METHODS The study included 54 patients who underwent (18)F-FDG PET and CT scans within 3 wk before initiation of imatinib mesylate therapy . Forty-nine of these patients underwent repeat scans 2 mo after therapy . The numbers of sites or organs containing lesions on (18)F-FDG PET and CT scans were compared . Corresponding lesions on (18)F-FDG PET and CT scans or those confirmed to be malignant in appearance by other imaging modalities or on follow-up were considered true positives . Lesions seen on (18)F-FDG PET or CT scans but not seen or confirmed to be of benign appearance with other imaging modalities or on follow-up were considered false positives . Measurements of the maximum st and ard uptake value ( SUV ) on (18)F-FDG PET scans and tumor size on CT scans were used for quantitative evaluation of early tumor response to therapy . RESULTS A total of 122 and 114 sites and /or organs were involved on pretherapy (18)F-FDG PET and CT scans , respectively . The sensitivity and positive predictive values ( PPVs ) for CT were 93 % and 100 % ; whereas these values for (18)F-FDG PET were 86 % and 98 % . However , the differences between these values for CT and (18)F-FDG PET were not statistically significant ( P = 0.27 for sensitivity and 0.25 for PPV ) . This suggests comparable performance of (18)F-FDG PET and CT in staging GISTs . Repeat scans at 2 mo after therapy showed agreement between (18)F-FDG PET and CT scans in 71.4 % of patients ( 57.1 % having a good response to therapy and 14.3 % lacking a response ) . Discrepant results between (18)F-FDG PET and CT were recorded for 28.6 % of the patients . (18)F-FDG PET predicted response to therapy earlier than did CT in 22.5 % of patients during a longer follow-up interval ( 4 - 16 mo ) , whereas CT predicted lack of response to therapy earlier than (18)F-FDG PET in 4.1 % . One patient did not undergo long-term follow-up . These findings suggest that (18)F-FDG PET is superior to CT in predicting early response to therapy in recurrent or metastatic GIST patients . CONCLUSION The performances of (18)F-FDG PET and CT are comparable in staging GISTs before initiation of imatinib mesylate therapy . However , (18)F-FDG PET is superior to CT in predicting early response to therapy . Thus , (18)F-FDG PET is a better guide for imatinib mesylate therapy AIM The aim of this study was to evaluate the utility of positron emission tomography with 18F-fluorodeoxyglucose ( FDG-PET ) in monitoring response in refractory GIST . METHODS This multicenter study prospect ively evaluated 21 patients with locally advanced and /or metastatic GIST refractory to with high-dose imatinib ( 800 mg/day ) treated with doxorubicin 15 - 20 mg/m2/weekly for 4 cycles , followed by imatinib maintenance ( 400 mg/day ) .  CT and FDG-PET were performed at baseline and after completion of therapy . RESULTS Mean baseline tumor size on CT was 5.9 cm . Median progression-free survival ( PFS ) was 219 days ( range 62 - 1108 ) . Three out of 21 patients ( 14 % ) had partial responses ( PR ) under RECIST criteria , 12 patients ( 57 % ) remained stable ( SD ) and 6 showed progression ( PD ) of the disease during treatment ( 29 % ) . Six patients had PR by FDG-PET , 15 showed SD ( n=9 ) or PD ( n=6 ) based on EORTC criteria . Patients with a PFS < 6 mo showed a significantly higher ∑SUVmax at baseline ( 26.04±13.4 ) than those with PFS≥6 mo ( 9.82±5.0 ) ( P<0.05 ) . A correlation was found between PET response and PFS : PR 14±6.1 mo , SD 5.5±0.8 mo and PD 3.5±4.1 mo ( P<0.05 ) . A residual SUVmax < 5 after treatment correlated with improved PFS ( 314±315 days vs 131±91 days ) ( P<0.01 ) . Survival curves showed a significant association between PET response and PFS ( P<0.05 ) . Patients with wild-type genotype KIT ( KIT-WT ) showed a significantly lower baseline SUVmax ( 5.36±1.4 ) than non-WT KIT ( 8.40±3.6 ) ( P<0.05 ) . CONCLUSION FDG-PET is useful in assessing response of GIST refractory to imatinib and correlates with the presence of KIT-WT . Baseline ∑SUVmax can predict response to treatment in this series Purpose This multicenter phase 2 study assessed the tolerability and efficacy of motesanib , an oral inhibitor of Kit , platelet-derived growth factor receptor ( PDGFR ) , and vascular endothelial growth factor receptors ( VEGFR ) , in patients with imatinib-resistant gastrointestinal stromal tumors ( GIST ) . Methods Patients with advanced GIST who failed imatinib mesylate after ≥8 weeks of treatment with ≥600 mg daily received motesanib 125 mg orally once daily continuously for 48 weeks or until unacceptable toxicity or disease progression occurred . The primary endpoint was confirmed objective tumor response per RECIST and independent review . Secondary endpoints included progression-free survival ( PFS ) , time to progression ( TTP ) ; objective response by 18FDG-PET and by changes in tumor size and /or density ( Choi criteria ) ; pharmacokinetics and safety . Results In the patients evaluable for response ( N = 102 ) , the objective response rate was 3 % ; 59 % of patients achieved stable disease , with 14 % achieving durable stable disease ≥24 weeks ; 38 % had disease progression . Higher objective response rates were observed per 18FDG-PET ( N = 91 ) ( 30 % ) and Choi criteria ( 41 % ) . The median PFS was 16 weeks ( 95 % CI = 14–24 weeks ) ; the median TTP was 17 weeks ( 95 % CI = 15–24 weeks ) . The most common motesanib treatment-related grade 3 adverse events included hypertension ( 23 % ) , fatigue ( 9 % ) , and diarrhea ( 5 % ) . Motesanib did not accumulate with daily dosing . Conclusions In this study of patients with imatinib-resistant GIST  , motesanib treatment result ed in acceptable tolerability and modest tumor control as evident in the proportion of patients who achieved stable disease and durable stable disease Summary Objectives To determine the quantitative parameters of DCE-US for predicting early functional response of patients with metastatic gastrointestinal stromal tumors ( GIST ) . Material s and methods Phase II multicentre clinical trial in patients with metastatic GIST treated with masatinib mesylate ( 7.5 mg/kg daily by oral route ) Patients followed using three different imaging techniques : 1 ) DCE-US before treatment and on days 1 , 7 , 15 and after 1 , 2 , 4 , 6 months and every 3 months . 2 ) CT assessment s , using RECIST criteria , before treatment , after 2 , 4 , 6 months and then every 3 months . 3 ) FDG PET before treatment and after 1 month . Results Twenty patients included and followed-up for up to 36 months , with 269 DCE-US examinations performed . No significant changes in the 7 selected DCE-US variables on day 1 and 7 vs baseline . On day 15 , significant reductions in all the variables related to blood volume recorded : area under the curve ( AUC ) ( p = 0 . 004 ) , area under the wash-in ( AUWI ) ( p = 0.002 ) , area under the wash-out ( AUWO ) ( p = 0.002 ) and Peak Intensity ( p = 0.005 ) . Also slope of wash-in changed significantly ( p = 0.003 ) . An important reduction in St and ard Uptake Values ( SUV ) recorded in 7/11 patients ( PFS > 18 months ) . Decrease in DCE-US AUC , AUWI and AUWO values on day 7 were predictive of PET-CT results . Conclusions AUC AUWI , AUWO are the DCE-US parameters related to blood volume that at D 15 can predict the response of GISTs to treatment with masatinib . Additional studies are ongoing PURPOSE The aim of this study was to identify factors predicting initial and late resistance of GI stromal tumor ( GIST ) patients to  imatinib  and to document the dose-response relationship in the prognostic subgroups . This study is based on the European Organisation for Research and Treatment of Cancer-Italian Sarcoma Group-Australasian Gastrointestinal Trials Group r and omized trial comparing two doses of imatinib in advanced disease . PATIENTS AND METHODS Initial resistance was defined as progression within 3 months of r and omization , and late resistance was defined as progression beyond 3 months . Investigated cofactors include imatinib dose , age , sex , performance status , original disease site , site and size of lesions at trial entry , and baseline hematologic and biologic parameters . RESULTS Initial resistance was recorded for 116 ( 12 % ) of 934 assessable patients and was independently predicted by the presence of lung and absence of liver metastases , low hemoglobin level , and high granulocyte count . Among 818 patients who were alive and progression free at 3 months , 347 subsequent progressions were recorded , and late resistance was independently predicted by high baseline granulocyte count , primary tumor outside of the stomach , large tumor size , and low initial imatinib dose . The impact of initial dose on late resistance was mainly significant in patients with a high baseline granulocyte count ( > 5.10(9)/L ) and in patients with tumors of GI origin outside of the stomach and small intestine . CONCLUSION Our study identifies patients for whom initial and /or long-term treatment needs to be improved and patients who require a high initial dose . Correlation of these results with immunohistochemistry and molecular parameters may further help to underst and the biologic mechanisms of resistance Background : Malignant gastrointestinal stromal tumours ( GISTs ) are a rare subset of aggressive mesenchymal tumours specific to the gastrointestinal system . They are both locally aggressive and can metastasize . The aim of this analysis was to report on our experience of the utility of coincidence positron emission tomography ( co-PET ) based on an 18F-FDG gamma camera in assessing treatment response to imatinib  using CT as the comparator and the final clinical outcome as the end point . Methods : We compared the results of CT and PET scans as predictors of outcome in a consecutive series of patients treated at the Prince of Wales hospital . All patients had biopsy-proven malignant GIST and were on treatment with the targeted pharmacotherapeutic agent imatinib . The majority of the patients were receiving treatment as part of the r and omized trial of the European Organization for Research and Treatment of Cancer , the Australian Gastrointestinal Trials Group and the Italian Sarcoma Group , comparing 400 with 800 mg ( 400 mg b.i.d . ) . The monitoring of tumour response was achieved by serial CT measurements according to the RECIST criteria . Concurrent 18F-FDG co-PET studies were performed within a mean of 2.8 days from the CT scan and were interpreted by a consensus panel of 2 nuclear medicine physicians . Results : A total of 18 patients were recruited into the study , with a total of 74 lesions . There were 47 liver lesions , 31 of which were identified on the initial 18F-FDG co-PET scans ( 63 % ) . There were 10 primary lesions ( 4 stomach , 4 duodenal , 2 small bowel ) , 9 of which were demonstrated on initial 18F-FDG co-PET examinations ( 90 % ) . There were 17 extrahepatic metastatic sites , 15 of which were visualized on the initial 18F-FDG study ( 88 % ) . Of the 18 patients , 8 showed concordant improvement on both CT and 18F-FDG co-PET criteria . One patient showed concordant worsening and 1 was not FDG avid . Eight patients initially showed discordance . 18F-FDG co-P 
    Output:
    
(18)F-FDG PET has a significant value in assessing treatment response to imatinib or other drugs in GIST patients .
(18)F-FDG PET allows an early assessment of treatment response and is a strong predictor of clinical outcome