Abstract:
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Purpose: GIST are rare mesenchymal tumours of the GI tract, mesentry or omentum. The majority stain positive for the c-kit gene (CD117) and GIST with c-kit mutations tend to show aggressive clinical behaviour and histological features. Recently, STI571 (a selective tyrosine kinase inhibitor) has been employed with success in recurrent and metastatic GIST. This poster will illustrate the varied appearance of malignant c-kit positive GIST at presentation and follow-up post treatment with STI571 ,and pictorially demonstrate complications of therapy with STI-571.
Methods and Materials: 15 patients (12 male:3 female), aged 26 to 83 years, (mean 67.4 years) with biopsy proven c-kit positive malignant GIST underwent selected radiological examination (CT, MRI, ultrasound, barium studies and PET) at baseline and at 3 monthly intervals post commencement of STI 571. Parameters studied included primary and metastatic tumour size, location, number, enhancement characteristics and activity as evidenced by PET. Coexistent complications of STI-571 therapy were searched for.
Results: 11 patients were commenced on STI-571 for metastatic disease at presentation and 4 patients for recurrent disease. Primary tumour location was: small intestine (7 patients), stomach (4 pts.), peritoneum (2 pts.), rectum (2 pts.). Partial response was seen in 11/15 patients (73.3%). Primary tumour size (11 patients) pre-treatment was 3.2 to 17.1 cm (mean 11.8cm) & 2.8 to 14.6cm (mean 8.8cm) at 6 months post treatment. Recurrent disease decreased in size in 2/4 patients. There were liver metastases at presentation in 7/15 patients, peritoneal metastases in 2/15 patients and both in 3/15 patients. At 6 months post commencement of therapy,liver metastases had decreased in size in 7/10 patients and in number in 2/10 patients. Peritoneal metastases had decreased in size in 3/5 patients and had not decreased in number in any patient. Lack of response to STI-571 was seen in 4 patients. Necrosis in the primary or recurrent tumour was seen in 6/15 patients during treatment. Initial increase in size of liver metastases after therapy was seen in 2/15 patients due to haemorrhage (not disease progression). Concurrent PET scanning revealed a decrease in liver activity in both cases. Transient ascites post commencement of STI-571 was seen in 2/15 patients.
Conclusion: STI 571 is an effective novel therapy in the management of GIST. Anatomical information does not always reflect biological behaviour. PET scanning is a useful tool in assessment of primary tumour and metastatic activity.
Johnston MD, C,
GI Stromal Tumours (GIST): Imaging Features Pre- and Post Treatment with STI571, a Novel Molecular Targeted Therapy. Radiological Society of North America 2003 Scientific Assembly and Annual Meeting, November 30 - December 5, 2003 ,Chicago IL.
http://archive.rsna.org/2003/3108138.html
