Cystic changes in hepatic and peritoneal metastases from gastrointestinal stromal tumors treated with Gleevec

Background: Tyrosine kinase inhibitor (Gleevee or STI-571) must be considered the treatment of choice for metastatic gastrointestinal stromal tumors (GISTs). The purpose of this article is to address and illustrate a longterm follow-up of computed tomographic (CT) radiologic findings in patients with metastases from GIST after Gleevec treatment. Methods: We performed a retrospective review of seven patients (four male, three female) with unresectable metastases from GIST who were treated with STI-571 in a 1-year period. Patients were followed every 2-4 months by contrast-enhanced CT for up to 12 months. The size and attenuation of hepatic and peritoneal metastases on CT were measured and correlated. Results: Hepatic metastases from GISTs showed significant decreased attenuation from a mean of 60 HU to a mean of 32 HU (p < 0.01) in the first 2 months and continued decreasing attenuation to 23 HU at the 12-month follow-up. These metastases superficially resembled simple cysts. Most metastases became smaller, with more defined borders, after treatment. Histologic examination in a resected specimen revealed hepatic cyst with no residual tumor cells, regression of omental lesions, and extensive necrosis. Conclusions: CT findings of unresectable hepatic and peritoneal metastases from GIST displayed decreasing, near cystic attenuation and size as an effective regression in response to STI-571 treatment.