Effect of Angiosonography to Monitor Response During Imatinib Treatment in Patients with Metastatic Gastrointestinal Stromal Tumors

Abstract

Gastrointestinal stromal tumor (GIST) metastases are typically intra-abdominal and hypervascular. We assessed the effect of angiosonography with a second-generation contrast agent to monitor response during imatinib treatment in patients with metastatic KIT+ GIST. Ten consecutive patients with known advanced KIT+ GIST were investigated with angiosonography and computerized tomography (CT). We also monitored the serum levels of the major angiogenic growth factor, vascular endothelial growth factor. Angiosonography showed a reduction in tumor vascularization of liver metastases during imatinib treatment in all cases. We observed a reduction in tumor vascularization before a reduction in tumor size. The tumor perfusion appeared reduced in the central part of the liver metastases. With a median follow-up of 18 months (range 3-33), a reduction in tumor vascularization was initially observed in all patients, but progressive disease was documented in four patients following imatinib treatment. CT documented tumor response according to standardized criteria in six patients, stable disease in four, and progressive disease according to angiosonography. The reduction of tumor perfusion at angiosonography correlated with the pseudocystic appearance at CT. The "nodule(s) within a mass" pattern of recurrence occurred in two patients with no difference observed between angiosonography and CT. Early decreasing serum vascular endothelial growth factor levels were observed in the two cases with higher pretreatment levels. Imatinib could induce antiangiogenic and/or antivascular effects in GIST, and this effect could be easily monitored with angiosonography. Angiosonography might be a useful complement for monitoring the therapeutic effect of imatinib in these patients.