Assessment of gastrointestinal stromal tumors with computed tomography following treatment with imatinib mesylate

Abstract

Aim: To evaluate and characterize the patterns of disease progression of metastatic or unresectable gastrointestinal stromal tumor (GIST) treated with imatinib mesylate, and to determine the prognostic significance associated with disease progression.

Methods: Clinical data and computed tomography (CT) images were retrospectively reviewed in 17 GIST patients who were treated with imatinib mesylate from October 2002 to October 2006. Apart from using size measurement for evaluation of tumor response [Response Evaluation Criteria in Solid Tumors (RECIST) criteria], patterns of CT changes during treatment were evaluated and correlated with clinical data.

Results: There were eight non-responders and nine responders. Five patterns of CT change during treatment were found: focal progression (FP), generalized progression (GP), generalized cystic change (GC), new cystic lesion (NC) and new solid lesion (NS). At the end of study, all non-responders showed GP, whereas responders showed cystic change (GC and NC) and response according to RECIST criteria. Overall survival was significantly better in patients with cystic change or response within the RECIST criteria compared with GP patients (P = 0.0271).

Conclusion: Various patterns of CT change in patients with GIST who responded to imatinib mesylate were demonstrated, and might determine the prognosis of the disease. A combination of RECIST criteria and pattern of CT change are proposed for response evaluation in GIST.

Figure 1

FP pattern. Contrast-enhanced CT of the abdomen obtained from a 39-year-old woman with metastatic GIST in the right lobe of liver. A: Before imatinib therapy, the lesion showed ill-defined thickened rim enhancement (arrow); B: After 2 mo therapy, a nearly complete cystic change and a thin lesion boundary were observed; C: After 5 mo therapy, a further decrease in size (partial response by RECIST) was seen; D: After 10 mo therapy, a small enhancing nodule was seen. Nodule within a mass or FP (arrow head).

Figure 2

GP pattern. Contrast-enhanced CT of abdomen obtained from a 55-year-old man with metastatic GIST in the mesentery. A: Before imatinib treatment, there were mesenteric masses (arrows); B: After 2 mo therapy, there was interval progression in both mesenteric masses, as demonstrated by increased tumor size and thickness of the enhancing wall (arrows).

Figure 3

NS pattern. Contrast-enhanced CT scan of abdomen obtained in a 39-year-old woman with metastatic GIST in the liver. A: Before imatinib treatment, a large subcapsular cystic lesion in the right hepatic lobe and a small amount of free fluid were noted; B: After 10 mo therapy, there were new, well-defined, homogeneous enhancing nodules adjacent to the gallbladder (arrow); C: After 13 mo therapy, there was a slight increase in size of the mentioned nodule (arrow).

Figure 4

GC pattern. Contrast-enhanced CT scan of the abdomen obtained in a 64-year-old man with metastatic GIST in both lobes of the liver (arrows). A: Before imatinib treatment, there were a few rather ill-defined, small homogeneous enhancing lesions in the liver (arrows); B: After 4 mo therapy, they showed better-defined, non-enhancing, low-density lesions; C: After 8 mo therapy, well-defined small cystic lesions with no interval change in size are noted.

Figure 5

NC pattern. Contrast-enhanced CT scan of abdomen in 50-year-old woman with metastatic GIST in the liver. A: Before imatinib treatment, no liver metastases were visible at this level; B: Contrast-enhanced CT after 2 mo treatment with imatinib. At least two non-enhancing low-density lesions were newly seen at the dome of the liver (arrows).

Figure 6

Overall survival after imatinib therapy, according to the patterns of CT change.