Gastrointestinal stromal tumours

Gastrointestinal stromal tumours (GISTs), previously classified as benign or malignant smooth muscle tumours, are the most common mesenchymal tumours of the gastrointestinal tract. GISTs express a growth factor receptor with tyrosine kinase activity, termed KIT. Mutations of KIT are common in malignant GISTs and lead to constitutional activation of tyrosine kinase function, which causes cellular proliferation and resistance to apoptosis. GISTs are notoriously unresponsive to chemotherapy and, until the recent introduction of the KIT inhibitor imatinib, there has been no effective therapy for advanced, metastatic disease.

A Medline literature search was preformed to locate all articles relating to gastrointestinal tumours, GISTs, KIT and imatinib.

The 5-year survival rate after complete resection of GISTs is approximately 50 per cent. The median duration of survival for patients with a metastatic GIST is approximately 20 months, and 9-12 months for patients with local recurrence. Phase II trials have investigated the effect of imatinib on irresectable or metastatic GISTs. In these trials more than 50 per cent of patients responded to imatinib within a few months and approximately 12 per cent had disease progression. Uptake of [(18)F]fluoro-2-deoxy-D-glucose demonstrated by positron emission tomography has been found to be reduced after starting imatinib. The potential for cure and the optimal length of treatment is currently unknown. Imatinib is the first effective systemic therapy for metastatic and locally irresectable GISTs. Large multi-institutional clinical trials to investigate the efficacy of imatinib as adjuvant or neoadjuvant therapy for GISTs are now required.