[Association of CT image changes and prognosis in gastrointestinal stromal tumor after targeted therapy]

To investigate the association between CT image changes and the prognosis in gastrointestinal stromal tumors (GIST) after targeted therapy.

A total of 35 patients with GIST were treated by imatinib mesylate from April 2003 to June 2008. The longest diameter (LD) and mean enhanced CT values (HU) of tumors were measured on axial images. The CT classifying (number, location, liver metastasis, hemorrhage,cystic degeneration) and quantitative indices (pre- and 2-6 months post-treatment LD, HU, and their change rate) were compared between those with and without progress in two years.

During follow-up (median:285 months) 13 cases had tumor progress. The progress rate was higher in the group with extensive tumor involvement (> or = 5 lesions and > or = 2 parts), and that without hemorrhage demonstrated. The mean change rate was -14.29% (range, -67%, 11%) for LD and -12.25% (range, -55%, 39%) for HU in non-progressive group, while the mean change rate was 15.09%(range, -45%, 191%) for LD and 9.91% (-27%, 135%) for HU in progressive group. The differences were significantly different (P<0.01). The accuracies of predicting 2-year progress by LD and HU change rates were moderate, with area under ROC curve being 0.790 and 0.797, respectively.

The 2-year progress rate of GIST after targeted therapy is higher in extensively involved tumors. Higher decrease rates of LD and HU predict less 2-year progress, which possess moderate prediction accuracy and can be used as valuable indicators in the evaluation of targeted therapy for GIST.